Yuu Mononobe
Yuu Mononobe Profile Image
Vital statistics
Name Yuu Mononobe
Kanji 物部 悠
Romaji Mononobe Yū
Gender Male
Birthdate December 25
Affiliation NIFL (formerly)
Status Alive
Occupation Second Lieutenant
Relatives Yoshimi Mononobe (Mother)
Kai Mononobe (Father)
Mitsuki Mononobe (Foster Sister)
Firill Crest (Wife only inside her country)
First appearance
Light Novel Debut Volume 1
Manga Debut Chapter 0
Anime Debut Episode 1
Seiyuu Yoshitsugu Matsuoka

Yuu Mononobe (物部 悠, Mononobe Yū) is the main protagonist in the Unlimited Fafnir series and the only male D in the world. He was formerly a Second Lieutenant at NIFL and captain of the Special Operations team Sleipnir. Upon his transfer to Midgard, he is assigned to Brynhildr Class as Student No 8 and later becomes a reserve member of the Dragon Subjugation Squad. He is later revealed to be the Ninth Dragon.


Yuu is a handsome, sixteen-year-old boy with rather messy, light blue hair, which is quite spiky. His eye color is almost the same as his hair. Yuu is usually clad in Midgard's school uniform, which is comprised of black-colored trousers, button shirt and blazer, which he usually wears unbuttoned, and a white tie. Yuu's back contains various scars he has sustained from certain battles. His dragon mark is located on the back of his left hand with two marks around it which appeared after he defeated Leviathan and Hraesvelgr respectively.


Yuu has a rather strong and straightforward attitude, willing to do anything to protect his friends and family from harm, even sacrificing his memories for their sake. He is also very obstinate once he has decided on something, as was noted by both Loki Jotunheim and Mitsuki Mononobe. He also tends to be brutally honest when he offers his opinion on something, believing that one will not learn from their mistakes otherwise. While Yuu usually keeps a calm and clear mind, he tends to exhibit perverted thoughts when around the girls he's close to, often blurring out what he finds attractive about them without reservation. This usually causes people to accuse him of lacking delicacy.

Being raised as a soldier, Yuu acts respectfully to those of higher rank than him, even saluting them out of habit. Yuu is also a very kind person and cares very much for his friends, a trait which has caused most of the girls in the series to develop feelings for him. However, when angered, Yuu is capable of exhibiting powerful killing intent, something which is more prominent when he's under the influence of his Fafnir persona. In this state, Yuu becomes a merciless killer, capable of exterminating any foe without exception. Although Yuu usually restrains himself from killing anyone, he has been shown to not hesitate in going for the kill in several occasions.


Yuu grew up in a small town called Nanato City alongside his neighbor and childhood friend, Mitsuki. The two were inseparable and would go everywhere together, with their most frequently visited location being a platform with a view of the entire town. It was there that Mitsuki declared her intention to marry Yuu, kissing him on the lips as a sign of their engagement.

One day, at age six, while going camping with Mitsuki's parents, they had a car accident which resulted in the death of her parents. Supposedly, he and Mitsuki survived due to the awakening of their abilities as Ds, but unbeknowst to Yuu, he actually became the Ninth Counterdragon due to encountering the Ninth True Dragon (the true cause of the accident), which he proceeded to seal inside Mitsuki. Mitsuki was later adopted into Yuu's family, much to her displeasure since she would not be able to fulfill her dream of marrying Yuu. However, Yuu reassured her that he still intended to keep their promise and asked Mitsuki to keep their new-found powers a secret.

Three years before the start of the series, at the age of 13, Yuu met Kili Surtr Muspelheim for the first time when the latter jumped off a bridge while trying to save a cat that had been following her. When he approached her with the intent of helping her, Kili gave him the cat (which was later named Ohagi) and warned him that the next day, Hekatonkheir would attack the city, much to his confusion. The following day, Hekatonkheir indeed appeared in Nanato City and started destroying it. Seeing that Mitsuki had not evacuated, Yuu sought her out, finding her in their observation platform trying in vain to fend off Hekatonkheir. After listening to Mitsuki's tearful outburst, Yuu was contacted by 'Green' Yggdrasil, who offered him the power to destroy the Dragon in exchange for his memories. Yuu accepted the deal and, after borrowing dark matter from Mitsuki, destroyed Hekatonkeir with an Anti-Dragon Armament.

Shortly after that incident, Yuu was separated from his family and was taken into NIFL custody, with his existence as the only male D being kept a secret from Asgard and the world in general. There, he was forced to become Major Loki Jotunheim's subordinate, with the latter implanting the Fafnir persona into him and training Yuu in order to make him the strongest assassin. Eventually, Yuu rose to the position of Second Lieutenant and became captain of Sleipnir, a Special Forces team with the purpose of eliminating Ds designated as disasters. While Yuu had the choice to either spare or kill his opponents, he never went as far as to murder anyone, no matter how difficult the mission was. During one of his missions, he saved the life of recently-added Sleipnir member Jeanne Hortensia (who was cross-dressing as a man and using the alias John), which led to Jeanne developing feelings for him. In another mission, he saved a young D called Tear Lightning from a criminal group. Instead of taking her into custody, Yuu let her go to be with her parents and warned her not to use her powers in front of other people again. Shortly before the start of the series, Yuu was transferred to Midgard under Mitsuki's orders.


Dragon's EdenEdit

Yuu was introduced in Volume 1, where he encountered a naked Iris Freyja on Midgard's beach. When Iris prepared to attack him, Yuu's Fafnir awoke and attempted to kill Iris. Yuu was barely able to suppress it through willpower and was surprised when Iris' attack backfired on her, knocking her unconscious. When she came to, Yuu hurriedly explained that he was not an intruder and that he belonged to NIFL. Before he could further refute Iris' accusations, the conversation was interrupted by Mitsuki, who led Yuu to her quarters. There, Yuu was informed that he would attend Midgard as a student, much to his surprise. The next day, Yuu was introduced to the school assembly and was subsequently placed in Brynhildr Class. Upon entering the class, Yuu was faced with opposition from Lisa Highwalker, forcing him to perform transmutation in order to prove his status as a D to the rest of his new classmates.

Yuu proceeded to join the rest of the class in a training exercise, where he saved Iris when her transmutation backfired on her and took her to the infirmary. While there, Iris told him about her motives for joining the Dragon Subjugation Squad. Yuu then suggested that they should train together until the selection test. During training under Mitsuki's supervision, Yuu's usual methods of attack and defense proved insufficient due to his low dark matter capacity, with Mitsuki advising him to should focus on creating a Fictional Armament. When Mitsuki noted that Iris' explosion was something that Ds could not do normally, Yuu suggested that Iris use this ability as a method of attack. During the selection test for the Dragon Subjugation Squad, Yuu was able to pierce the target diamond by accidentally creating plasma, and was thus listed as a reserve member. When Iris succeeded in destroying the diamond with her explosion, Yuu congratulated her. Later on, he was called out by Iris to meet her at the beach, where he explained that he helped because she reminded him of the past Mitsuki. Before they could continue, the alarm sounded, warning everyone that 'White' Leviathan was approaching the island.

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Yuu is contacted by Loki

Upon returning to his room, Yuu was contacted by Major Loki Jotunheim, who asked him to kill the D targeted by Leviathan in order to prevent an increase in Dragons. Although Yuu was reluctant, Loki warned him that he would have to resort to less efficient means should he refuse. During school assembly, Yuu noticed that Iris was absent and started searching for her, eventually finding her on the school building's roof. After he asked her to show him her dragon mark, Yuu confirmed that Iris was targeted by Leviathan due to the mark having changed its color. Although Iris was afraid, Yuu reassured her that if it came down to it, he would kill her himself, declaring himself to be the world's strongest assassin, much to Iris' amusement. Afterwards, Yuu approached Mitsuki and requested to be assigned as Iris' bodyguard in order to restrain NIFL, revealing to her what Major Loki told him. Mitsuki agreed on the condition that she would kill Iris if the worst came to pass. Although Yuu protested, he was silenced when Mitsuki stated that her hands were already dyed with blood. When he met with Lisa outside of Iris' room, she revealed to him that during 'Purple' Kraken's attack two years ago, Mitsuki was the one who eliminated both Krakens, one of which was a dragonified Miyako Shinomiya. While guarding Iris, Yuu was forced to endure several stimulating situations, ranging from Iris entering the bath to wash his back to the two of them sleeping in the same bed.

After Leviathan broke through the defense lines, Yuu was summoned to the command center
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Yuu and Iris confront Mitsuki

by Haruka Shinomiya, who explained that she had allowed NIFL troops to land on Midgard in order to kill Iris as a way of preventing anyone else from shouldering the responsibility. Yuu declared that he would drive away the soldiers and headed towards their invasion route along with Iris. Upon locating them, he engaged them in combat, incapacitating half of them by utilizing his Fafnir persona, something which forced the rest to retreat. While heading to confront Leviathan, Yuu and Iris were stopped by Mitsuki, who was determined to kill Iris since Leviathan could not be stopped. In order to settle this matter, Yuu fought with Mitsuki and won by lightly chopping her head like how they did when they were young. Following that confrontation, Iris a
V1 I10

Iris kisses Yuu out of gratitude for saving her

ttacked Leviathan with her explosion and Yuu constructed an Anti-Dragon Armament by borrowing dark matter from Mitsuki. However, their attacks proved insufficient against the Dragon. Seeing that Iris would not give up, Yuu reconnected with Yggdrasil, downloading additional data for a new weapon, while also losing more of his memories. With Iris' aid, Yuu constructed the Marduk Main Cannon, Babel and, with the aid of the Dragon Subjugation Squad, succeeded in destroying Leviathan. The next day, Yuu was congratulated by Major Loki for his performance and was promoted to the status of 'probationary classmate' by Lisa as thanks for his efforts. Yuu then met Iris on the beach, who asked to be his friend. After replying to her that he already thought of them as friends, Iris kissed him as a sign of her gratitude for everything he had done.

Scarlet InnocentEdit

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Tear hugs Yuu upon meeting each other again

In Volume 2, Yuu was introduced to the principal of Midgard, Charlotte B. Lord, and her attendant, Mica Stuart. Charlotte examined his dragon mark and tried to rope him into joining her to peek at girls, much to his embarrassment. Afterwards, Yuu was informed alongside the rest of his classmates that the reason for the examination was to check whether the color of any student's dragon mark had changed, since 'Red' Basilisk was moving out of its habitat in search for a mate. At lunch break, during Brynhildr Class' conversation, Yuu explained to Iris that some Ds used their powers for evil and were classified as disasters, while hoping inwardly that Basilisk's target was not such a person. When Honoka Tachikawa and Tear Lightning were introduced in the school assembly one week later, Yuu stepped forward to calm the raging Tear and was surprised when the young D seemed to recognize him and declared him her husband. Seeing that he was the only person she would open up to, Tear was left to Yuu's care by Haruka. Yuu had a difficult time with Tear due to the fact that she refused to be apart from him and because she considered herself to be a dragon, refusing to comply with the rules of Midgard. After discussing with Tear, Yuu managed to convince her to open up to her classmates. However, while practicing how to form a Fictional Armament with Lisa's help, Tear's deeply-rooted belief that she was a dragon caused her to manifest a dragon-shaped armament which went berserk. Yuu was forced to work together with his classmates in order to stop Tear. While he was in the infirmary watching over Tear, Yuu encountered Honoka, who had been injured in a transmutation practice, and helped her to treat her wound, while also having a friendly conversation with her. Immediately after Honoka left, Yuu was contacted by Major Loki, who warned him that the Sons of Muspell and their leader, Kili Surtr Muspelheim, were planning to retrieve Tear, while also subtly reassuring Yuu that NIFL would not make any moves.

When Tear woke up, Yuu brought her to the beach in order to discuss with her. While Tear insisted that she and all Ds were dragons, Yuu countered by explaining that all Ds in Midgard had chosen to live as humans and asked Tear to tell him what happened to her parents. Upon hearing her story, Yuu was shocked to hear that Kili had killed Tear's parents. Although he now understood her circumstances, Yuu expressed his hope that Tear would choose to live as a human. He then proceeded to call their classmates, asking them to gather at the beach in order to have fun. The beach party and subsequent barbecue proved to be a big success. However, at the same night, Hekatonkheir suddenly appeared in Midgard. Yuu immediately headed out to intercept the Dragon with Mitsuki and Iris, leaving Tear behind under Lisa's protection. While waiting for the right moment to deploy his Anti-Dragon Armament, Yuu realized that Hekatonkheir was a diversion and hurried back to Tear's location.

He arrived just in time to save Lisa from Honoka's attack, who revealed that she was actually Kili in disguise. After a brief conversation, Yuu engaged Kili in combat. Although he was outmatched at first, Yuu turned the tables by awakening his Fafnir and wounding Kili in the abdomen. When Hekatonkheir became active again, Kili retreated, with Yuu asking her what exactly she was and Kili asking him in turn to decide for her. Yuu was shortly joined by the rest of his classmates, who launched a barrage of attacks against Hekatonkheir to no avail. At that moment, Yggdrasil granted Yuu access to Leviathan's ability, enabling him to levitate Hekatonkheir, which allowed the girls to push the dragon towards the sea. By borrowing dark matter from Tear, Yuu constructed the Special Artillery, Megiddo and destroyed Hekatonkheir with it. After he confirmed that Charlotte and Mica were safe, Yuu fainted due to blood loss from an earlier injury. While in the infirmary, Yuu was visited by Tear, who kissed him on the cheek as proof of their 'engagement', resulting in an argument between Iris and Tear. After Mitsuki sent out all the visitors, she asked whether it was true that he and Iris kissed. Yuu confirmed it, but when Mitsuki asked him to forget their childhood promise, Yuu replied that he would not forget it. He also resolutely stated that he would do whatever it took to end Mitsuki's battle against the dragons (which she used as penance for her act of killing Miyako), declaring that he would not give up on her happiness.

Crimson CatastropheEdit

After it became known that Basilisk was approaching Midgard in Volume 3, Yuu was informed by Mitsuki that he would probably not participate in the operation against the dragon, much to his surprise. However, after pointing out that the abilities he inherited from Leviathan might be of use, Haruka agreed to let him take part in the operation after testing his ability to create anti-gravitational matter. As the results of the test were positive, Yuu was allowed to join the Dragon Subjugation Squad. En route to the island selected as the battlefield by ship, Yuu, along with Tear and Ariella, chanced upon an argument between Lisa and Mitsuki about the matter of Miyako's death. While resting in his cabin and thinking about this matter, he was visited by Firill Crest, who demanded the book he had previously confiscated from her. Yuu took this opportunity to ask her about Lisa and Mitsuki's situation, with Firill informing him that Lisa did not resent Mitsuki at all. Their conversation was interrupted by a displeased Mitsuki, who thought that Yuu and Firill were engaging in an inappropriate relationship. After calming her down, Yuu asked her to sleep in the same room with him because she wished to discuss with her. When Mitsuki joined him that night, Yuu asked her about Miyako and the battle against Kraken two years ago. After hearing Mitsuki's account, Yuu asked her to look things from Lisa's perspective and persuaded her to seek Lisa's forgiveness.

V3 I5

Firill embracing Yuu at the Hot Springs

Upon arriving at the volcanic island, Yuu was confronted by an angry Lisa, who demanded to know if he had told something to Mitsuki. Yuu confirmed this and stated his belief that Mitsuki would clear any condition Lisa would offer. After Lisa left, Firill showed up, having heard everything, and promised him a reward, which turned out to be a ticket for the exclusive use of the island's hot spring. Yuu visited the hot spring the same night, but was horrified when his classmates started entering the spring, forcing him to hide. While concealing himself, Yuu was discovered by Firill, who explained to him that allowing him to see the naked bodies of the girls was also part of the reward, much to his embarrassment. His presence was almost exposed when Tear, who also discovered Yuu, made a ruckus, but an emergency call saved him. After everyone gathered back at the ship, Haruka informed them that NIFL would execute their operation tomorrow and that Basilisk's ability had been identified. The next day, Yuu and his classmates gathered on the bridge to watch NIFL's operation. Although Major General Dylan was confident that the Mistilteinn bomb would destroy the dragon, everyone was shocked when Basilisk evaporated it by using an enhanced version of Catastrophe. After NIFL's failure, Yuu started training along with everyone else in preparation for Midgard's operation. During his spare time, Yuu visited Iris' room and tried to express his feelings for her, but was stopped by Iris, who asked him to wait until the battle's conclusion. During Midgard's operation, Yuu was placed on standby and viewed both failed attempts to destroy Basilisk. When Ren and Mitsuki were about to be killed by Basilisk's Catastrophe, Yuu saved them by using his antigravity bullet to generate a repulsive field and bend the beam. Afterwards, the Dragon Subjugation Squad retreated.

V3 I7

Yuu hugging Mitsuki

Although things seemed hopeless, Yuu was able to discern a weakness in Basilisk's ability and proposed a new plan based on the assumption that the Dragon could not fire the enhanced version of Catastrophe for more than five seconds. Yuu contacted Major Loki and requested Mistilteinn's prototype for the new operation, which was delivered to them thanks to Major General Dylan. However, a problem arose when Mitsuki announced her intention to descend along with Mistilteinn. Yuu and the rest proceeded to volunteer as well and it was decided that the entirety of Brynhildr Class would descend with the bomb. That night Mitsuki came to Yuu's cabin discussing about the upcoming operation, the two hugged and promised to protect each other and come back alive. The operation was successful and Basilisk was destroyed. In the aftermath of the D
V3 I10

Yuu reveals his secret to Iris

ragon Subjugation Squad's victory, Yuu was visited by Tear, who declared her love for Yuu. Although surprised, Yuu explained to her that he liked someone else, only to be stunned by Tear's declaration that she would pursue Yuu and make him fall in love with her. After singing her to sleep, Yuu was approached by Mitsuki. During their brief conversation, Yuu was shocked to discover that he had forgotten that he and Mitsuki were not related by blood, as well as the promise of engagement between them. Upon returning to his cabin, Yuu found Iris waiting for him. Unable to contain himself, Yuu confessed that he loved Iris, but was not sure if his feelings were genuine, explaining to Iris everything about his contract with Yggdrasil and his lost memories.

Spirit HowlingEdit

In Volume 4, Yuu was very surprised once he found out that Firill was the granddaughter of the recently-deceased Albert Crest, monarch of the Principality of Erlia, and thus, a princess. When it was announced that Kili had sought refuge in Erlia and requested for Midgard to send Ds to pick her up, Yuu was sent to Erlia along with the rest of his classmates and Haruka. Upon arriving at the royal palace, Yuu was contacted by Major Loki, who asked him to eliminate Kili. Yuu refused, stating that this would go against Midgard's orders, but was concerned when Loki remarked that it might be a good opportunity for Yuu to become the complete Fafnir if he were to try and stop them. Later on, Yuu joined the girls in meeting with Firill's parents and Kili. After discussing tomorrow's schedule with Kili, Yuu was surprised and concerned to hear from her that Sleipnir had been deployed into this country along with Hreidmar, the originator of Yuu's Fafnir.

V4 C1

Yuu dancing with Kili

The next day, Yuu, along with Kili and the rest of the girls, went sightseeing around Erlia. When Kili was attacked in the middle of the city, Yuu joined her in fighting off her attacker, which turned out to be Jeanne Hortensia (who was crossdressing as a male called John). After Jeanne was subdued by Ariella, Yuu questioned her, confirming that Hreidmar had indeed been deployed to eliminate Kili, and then let her go. During the ball followng King Albert's funeral, Yuu danced with Kili, explaining to her about Hreidmar and his connection to him. Upon asking Kili what exactly she was, she dodged the question and left, promising to speak with him later. After dancing with Tear, Iris, Mitsuki and Lisa, Yuu sought out Kili again. While dancing with her in the courtyard, Yuu was shocked to find out that Kili had been created through biogenic transmutation from 'Black' Vritra. However, Yuu resolutely declared his belief that Kili was human due to the fact that he could kill her, promising not to reveal what she told him unless she chose to live as a dragon. At that moment, Hreidmar appeared and engaged Yuu in combat. Due to the fact that he was unwilling to fully surrender to his Fafnir persona, Yuu found himself in a severe disadvantage and was wounded. However, their battle was interrupted due to the arrival of 'Yellow' Hraesvelgr, who had come to claim Kili as its mate, forcing Hreidmar to retreat.

Yuu and Kili proceeded to rendezvous with the rest of the Dragon Subjugation Squad. After leaving Firill to protect Kili, Yuu and the rest attempted to intercept Hraesvelgr, but their attacks proved to be ineffective against the Dragon, who paralyzed everyone by using its Ether Wind. However, Hraesvelgr rejected Kili and set its sights on Firill. When Albert's soul manifested to protect Firill, Hraesvelgr consumed it and left. In the aftermath of the battle, Yuu was visited by Ariella, who pointed out Firill standing outside and asked him to go to her. Upon hearing a part of Ariella's harsh past, Yuu promised to listen to her story one day, before heading out to find Firill. Yuu was able to give some comfort to Firill with his words, but was shocked when Firill's dragon mark started changing color due to Hraesvelgr selecting her as its mate. While everyone was dejected over the fact that they could not come up with effective countermeasures against the dragon, Yuu reassured Firill that he still had a method he hadn't tried. Afterwards, Yuu visited Iris in her room and informed her of his decision to borrow Yggdrasil's power once again to overcome Hraesvelgr, despite Iris' objections. Following Iris' suggestion, Yuu started recounting the memories that he could still recall to her. Before he left, Iris kissed him, asking him to at least remember that kiss, which he promised to do. When the Dragon Subjugation Squad assembled, Yuu asked everyone to trust him when he declared he stll had a trump card and asked Firill out on a date with the intent of eliminating NIFL's interference before the battle.

The next day, Yuu and Firill were attacked by Hreidmar while walking in town during their 'date'. By utilizing his Fafnir more effectively than before, Yuu was able to defeat Hreidmar this time, but was surprised when he found out his armor was empty following his demise. Yuu then warned the concealed Sleipnir that he would show them no mercy if they tried to harm Firill. Afterwards, the two of them rendezvoused with the rest of the Dragon Subjugation Squad in the Great Waterfall of Erlia. When Hraesvelgr started approaching, Yuu reconnected with Yggdrasil and, after finding the necessary data, formed the Psionic multi-barreled cannon, Noah by borrowing Mitsuki's dark matter.
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Iris stating to Yuu that she will recover his memories

After seeing that one turret was not enough, Yuu borrowed dark matter from Iris and Firill to construct two more Noahs. With a combined attack from the three turrets and the Dragon Subjugation Squad, Hraesvelgr was vanquished, with Yuu losing consciousness afterwards. Upon waking, Yuu received congratulations from Major Loki and was visited by Firill, who declared that she now saw him as her prince, much to his embarrassment. However, Yuu was shocked to find out that he had forgotten all the memories from his birth up until the time he was picked up by NIFL. After explaining the situation to Iris, he was surprised when she resolutely declared that she would find a way to retrieve his memories, even if it meant she had to defeat Yggdrasil.

Midgard's CarnivalEdit

In Volume 5, Yuu was surprised by how much his popularity had increased after the victory against Hraesvelgr. During class, Yuu was informed by Haruka that Iris was sick and that Midgard would hold its first school festival a month later. Afterwards, he was sent to Charlotte's office, where she asked him to check whether he could perform new transmutations. Yuu did so, finding out that he could now replicate Hraesvelgr's Ether Wind, although this raised the question of who had inherited Basilisk's ability. After he got measured by Mica, Yuu was then sent out. When he visited Iris in her room to check up on her, Yuu discussed the matter of his lost memories with her, with Iris suggesting that he should ask for someone else's help as well. The next day, Brynhildr Class decided on setting up a Japanese teahouse for the festival, with Yuu and Lisa being selected as members of the festival executive committee.

While planning things for the festival alongside Lisa, Yuu was surprised to hear that she was the heiress to a large business conglomerate. Upon seeing that Lisa was troubled, Yuu was insistent on helping her, despite the fact that Lisa wanted to help him with his own problem first. Eventually, Lisa decided to accept Yuu's help and asked him to be her boyfriend for a day, much to his surprise. Yuu decided to accept her request after Lisa explained to him that she would be able to postpone choosing a fiancée with this. However, due to the fact that Yuu was unable to act intimately with Lisa, she decided that the two of them should do special training in order to get accustomed to acting like a couple. The following day, the two of them journeyed to Lisa's favorite spot in Midgard, succeeding in getting closer while spending their time there. During that time, Yuu revealed to Lisa the deal he had made with Yggdrasil and the loss of his memories. Although Lisa was angry, she promised to do whatever she could to help him, starting from investigating Yggdrasil. While Yuu planned to do the same, Yggdrasil exerted its influence over him to erase his suspicions. The next day, after supervising the cooking practice of Brynhildr Class, Yuu met with Lisa, who explained to him the nature of Yggdrasil's powers and warned him not to summon it lightly from now on.

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Yuu disguised as a girl

Two weeks later, Yuu was shocked to learn from Haruka that both Yggdrasil and Hekatonkheir had disappeared after engaging in combat. Upon discussing this new development with Lisa and Iris, Yuu stated that he was fine and tried to contact Yggdrasil with no success. While testing his Ether Wind later on, Yuu was shocked to hear from Charlotte that he would have to disguise as a girl since the world was largely unaware of his existence as the sole male D. He was also surprised when Charlotte suggested that other Dragons might be lurking in the world apart from those already known. While touring the school festival with Lisa and Tear, Yuu encountered Major Loki, who asked for a word with him. After leading him to the roof, he was attacked by Loki, who restrained him and declared that Yuu belonged to him, addressing an unidentified existence. In response, Yuu's left hand moved on its own and attempted to kill Loki, only to be interrupted by Lisa's arrival. After Loki left, Yuu collapsed on the spot and was sent to the infirmary

The following day, Yuu and Lisa explained to everyone about how the two of them would act like a couple for the day in order to fool Lisa's parents. The subsequent meeting was a success, although Yuu discerned that Lisa was sad over the fact that she would eventually have to choose a suitor. Changing the subject, Lisa explained to Yuu her findings about Yggdrasil and the state of Yuu's mind. When she stated that Yggdrasil might have transferred something akin to a computer virus in his mind, Yuu's left hand started moving on its own and attempted to strangle Lisa, revealing that Yggdrasil was indeed trying to take control of his body. Yuu attempted to blow off his hand by generating dark matter, but the dark matter turned into a vine instead. Fortunately, thanks to the timely arrival of Charlotte, Yuu was liberated from Yggdrasil's control, although the vine escaped into Midgard's grounds. After questioning Charlotte about her true identity, Yuu was surprised to find out that she was one of the Dragons, 'Gray' Vampire.

After Charlotte's explanations, Yuu headed to the command center with his classmates and Charlotte in order to discover Yggdrasil's whereabouts. Upon hearing that Iris, Tear, Ren and Lisa's parents had been captured, Yuu headed out with the rest of Brynhildr Class in order to rescue them. Thanks to Lisa's cover fire, Yuu was able to retrieve the hostages. However, Yggdrasil's power over electricity and its ability to steal dark matter made fighting it impossible. When Yggdrasil attempted to kill Iris, Yuu shielded her with his body, getting pierced i
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Yuu concerned over the possibility of Iris transforming into a Dragon

n the abdomen as a result. After Iris destroyed Yggdrasil with her new-found Catastrophe, Yuu fainted from blood loss. In the aftermath of the battle, Yuu awoke in the infirmary, where Charlotte revealed that she had used her abilities to accelerate his healing and informed him that Yggdrasil had reappeared in Japan. When his classmates visited him, Yuu was surprised to hear from Mark Highwalker that he now recognized him as a prospective suitor for Lisa. However, when Iris spoke to him, Yuu was reminded of what Charlotte told him previously, namely that it was possible Iris might turn into a Dragon due to the unnatural manner she had used Catastrophe.

Emerald TempestEdit

V6 I1

Yuu is embraced by Charlotte

In Volume 6, Yuu was still recuperating in the infirmary from the wounds he received from Yggdrasil, playing Japanese chess with Charlotte in order to pass the time. When they started conversing about the possibility of Iris becoming a Dragon, Yuu vehemently declared that Iris was human. However, he was embarrassed when Charlotte asked him to drop the polite tone towards her immediately afterwards. The next day, Yuu was forced to greet Charlotte with her nickname, Charl, and found himself in the unpleasant position of having to explain to his recently arrived classmates Charlotte's misguiding parting words. Four days later, Yuu was dispatched to Asgard’s First Laboratory in Japan alongside the rest of his classmates in order to test out a plan that had been proposed in order to combat Yggdrasil.

Upon arriving in Tokyo, Yuu was introduced to Kenya Miyazawa, director of the laboratory. After preventing Ariella from attacking him, Yuu was surprised to find out that she was his adopted daughter and that Ren was his biological daughter. However, shortly after everyone settled down, an explosion shook the building, which was revealed to be the work of Kili. Yuu was very surprised to see her again and was even more surprised to see that Jeanne (in her male disguise as John) was accompanying her. Although he questioned their purpose and partnership, he wasn't able to get any answers as the two swiftly retreated. Following that incident, the entire Brynhildr Class assembled in a conference hall, where director Miyazawa explained the true nature of Yggdrasil and his plan to defeat it, which involved materializing its soul through Yuu's Ether Wind and then destroy it by using Yuu's Noah. In order to make this plan feasible, Yuu started practicing dark matter transfer with Ren for the purpose of generating enough Ether Wind to materialize Yggdrasil's soul. However, his inability to connect with Ren hampered the process. In order for Yuu to better understand Ren, it was decided that everyone would visit an amusement park, where the two of them would communicate as much as possible.

The next day, Brynhildr Class headed to an amusement park in Tokyo, where Yuu was surprised to find out that everyone apart from him had talked with Ren at some point. After having fun in various attractions, Yuu was approached by Ariella, who explained to him her and Ren's past with Kenya Miyazawa. When the rest of the class made it so that Yuu and Ren would be alone in the ferris wheel, Yuu took this opportunity to explain everything about his deal with Yggdrasil and the loss of his memories to Ren so that she could understand him better. After asking Ren several questions, he was surprised when she asked him for permission to refer to him as 'Onii-chan', but readily consented. While everyone was heading for the exit, however, Tear was abruptly abducted by Jeanne, with Yuu chasing after them. After entering a mirror maze, Yuu confronted Jeanne and demanded for Tear to be returned. However, she refused to do so until Tear and Kili finished their conversation, leading to a fight between the two. Despite the fact that Yuu was superior, Jeanne's excellent eyesight, which allowed her to easily observe his movements in the mirror maze, evened the odds. However, the battle was interrupted with the conclusion of the talk between Tear and Kili. After Jeanne led Yuu to them, he demanded an explanation from Kili, who advised him that fighting Yggdrasil with their current method was futile and revealed the truth behind Hekatonkheir's origins.

After returning to the lab, Yuu informed Iris about how she used Catastrophe without going through dark matter conversion, warning her to keep this ability a secret. However, he was flustered when Iris asked him to check her body for signs of Dragon transformation. Just as the two were about to kiss in the heat of the moment, Yuu received a call for Kenya Miyazawa, who requested his presence at his underground lab. Upon arriving there, he was surprised when director Miyazawa asked him to test his Ether Wind by firing it on a human cadaver. Following the success of the experiment, Yuu attempted to talk to Kenya about Ren, but was unceremoniously sent away. While practicing with Ren the following day, Yuu asked her to assist him in participating in Kenya's experiment, hoping that the cadaver belonged to Ren's mother and that father and daughter might be able to reconcile. When his assumption was proven false, Yuu was outraged when Kenya announced that he couldn't love Ren, but was then surprised when Ren declared her hatred for Kenya and her desire to become closer to Yuu. At that moment, an alarm sounded, with Kenya announcing that Yggdrasil's branches were extending, expanding its interference range.

After joining his classmates, Yuu was forced to remain on standby while the rest of the Dragon Subjugation Squad dealt with Yggdrasil's expanding branches, allowing everyone to slowly approach the Dragon's main body. While discussing their current state with Lisa, Yuu revealed to her that Yggdrasil's interference on him was increasing, meaning that he could not retreat. A while later, Yggdrasil suddenly started growing even faster, forcing everyone into a tight spot. At that moment, Kili appeared, revealing that Yggdrasil had captured Vritra and was currently using her as an energy source. When Yuu suggested that they should retreat, he was met with Tear's objection, who had eavesdropped on his conversation with Lisa. This forced Yuu to reveal his condition to everyone, although he was able to keep the part about his lost memories secret thanks to Lisa's intervention. When Tear volunteered to have her horns undergo the final treatment at Kili's hands in order to give them a fighting chance, Yuu protested, but was prevented from interfering by Kili. Thanks to Tear's newfound abilities, the Dragon Subjugation Squad was able to approach Yggdrasil's main body and inflict damage on it unobstructed. Upon arriving there, Yuu borrowed dark matter fro
V6 I10

Yuu is informed by Tear that she can restore his memories

m Ren in order to generate enough Ether Wind to materialize Yggdrasil's soul, but despaired upon witnessing how enormous it was. Shaking off his hesitation, Yuu created the Noah turret and launched shell after shell, but was unable to inflict significant damage and was soon left drained. However, by borrowing mental power from his comrades, Yuu was able to fire a powerful shell that inflicted enough damage to Yggdrasil to allow Tear to hack its core, becoming the new core of Yggdrasil in the process. In the aftermath of the battle, when Tear announced to him that she was able to restore his memories, Yuu felt fear over the fact that his feelings for Iris might change with the return of his memories.

Black NemesisEdit

In Volume 7, after hearing from Tear that she could restore his memories, Yuu asked her to give him some time before attempting it. Upon arriving at the Asgard lab, Yuu was surprised to see that it was wrecked and asked Kili to leave so that she wouldn't be caught by NIFL's troops in the area. Due to the destruction of the lab, it was decided that Brynhildr Class would visit Yuu and Mitsuki's hometown, causing Yuu to feel anxious due to his lost memories. Upon arriving at his house, Yuu was reunited with his parents, Yoshimi and Kai Mononobe, and his pet cat, Ohagi. That night, Yuu invited Iris into his room and revealed to her that Tear was able to restore his memories, with Iris asking him to take her on a date before he retrieved his memories, something which he consented to.

V7 I5

Tear restores Yuu's memories

The following morning, Yuu and Iris had a brief date, which ended with the two of them kissing. After Mitsuki spotted them, Yuu was forced to explain everything regarding his lost memories to her, Ariella and Firill, with the latter two having arrived alongside the rest of their classmates. Upon receiving a kiss on the lips from Tear, Yuu's memories were unblocked, enabling him to recall scenes from his past. However, at that moment, 'Black' Vritra made her appearance over the skies of Nanato City in her Dragon form. Upon assuming a human form, Vritra expressed her hostility towards Yuu due to the fact that he had destroyed her Hekatonkheir with his Anti-Dragon Armaments twice, but did not attack him due to Tear's warning. After a brief discussion with Vritra, it was decided that everyone would tour Nanato City in order to help Yuu recall his memories, roping Vritra into joining them.

During the visit to the observation platform that Yuu and Mitsuki frequented as children, Yuu was able to finally recall his promise of marriage with Mitsuki, but was pressured by Mitsuki to choose Iris as his girlfriend. Iris, on the other hand, insisted that Yuu should choose Mitsuki, resulting in an argument between the two, which was interrupted by the arrival of the rest of the girls. On the way back home, Yuu suddenly recalled his first meeting with Kili three years ago and rushed to the spot, where he found a battered Kili and an unconscious Jeanne, much to his surprise. However, after Kili fainted, he was shocked when he noticed that her dragon mark had started changing color. After bringing the two of them home, Kili informed Yuu that she had been attacked by the Kraken's offspring, Kraken Zwei. At that moment, Haruka contacted everyone, informing them that Zwei was approaching Nanato City.

Leaving behind Firill, Tear and Lisa to watch over Vritra, Kili and the unconscious Jeanne, Yuu headed with the rest of the girls to a NIFL base. After they were briefed by Haruka, Yuu and the girls headed towards Kraken Zwei's location. Following Mitsuki’s inability to kill her with her antimatter arrow, Yuu led the girls in trapping Zwei inside a mithril-covered hole. In the aftermath of the battle, Yuu went to console Mitsuki and was asked by her to kiss her in order to realize that he truly loved Iris. However, before they could, an emergency message from Lisa notified them that Vritra had escaped and was targeting Mitsuki in an attempt to remove the only person who could pose a threat to Kraken Zwei.

Yuu proceeded to join with the rest of the Dragon Subjugation Squad and engaged Vritra's dragon stand-in in battle. Although Vritra appeared to have been destroyed after self-destructing, she emerged in her human stand-in and lightly wounded Mitsuki. Yuu attempted to convince her to surrender by threatening to destroy her with his Anti-Dragon Armament, but upon seeing Mitsuki collapse from Vritra's poison, Yuu almost killed
V7 I10

Vritra reveals her objective to Yuu

Vritra by using his Fafnir, only stopping because of Iris' plea. When Vritra was restrained by Tear, Yuu threatened her once more, asking her to give him the antidote to the poison. He was surprised when Vritra stated that Mitsuki would only sleep for a couple of days, but was shocked upon witnessing the girls' dragon marks changing color as a result of their encounter with Kraken Zwei. When Yuu called Vritra's actions meaningless and declared his intent to kill Zwei, he was surprised when Vritra admonished him for extinguishing humanity's potential and revealed that her plan was to have humans evolve into Dragons.

Amethyst RebirthEdit

In Volume 8, following a call from Kenya Miyazawa, Yuu and his classmates were forced to relocate to a mountain villa in order to protect those whose dragon marks had changed color from NIFL, bringing the restrained Vritra with them. Upon arriving there, Yuu was reunited with Lisa, Kili and the now conscious Jeanne, and was shocked to hear from Jeanne that Kraken Zwei had briefly treated her as a parent. After hearing the news that Kraken Zwei had escaped from its makeshift prison and having everyone's dragon marks checked, Yuu and company started discussing countermeasures against the hybrid. Eventually, it was decided that they should attempt to persuade Zwei first, with Yuu, Jeanne and Haruka being selected for this mission.

After checking up on Mitsuki, Yuu rushed downstairs upon hearing the perimeter alerts go off and was alarmed when he heard from Haruka that multiple intruders were approaching the villa. When asked by Haruka, Yuu expressed his opinion that they should intercept them, declaring that he would not lose to them as long as they were humans. Following a brief discussion, Yuu allowed Jeanne, Kili and Lisa to accompany him and act as support. Upon spotting the attackers, Yuu injured one of them, but was surprised to find out that they were humanoid drones. Sensing a person's presence in the forest, Yuu moved towards it. On the way, he was contacted in a private channel by Jeanne, who informed him that she had deserted NIFL to find out the truth behind Hreidmar. She then reported her findings to him, namely that Hreidmar had no physical body and that there were multiple people with that codename. At that moment, Yuu came across Hreidmar and engaged him in combat, easily defeating him due to his newfound mastery of his Fafnir. Upon Hreidmar's destruction, Yuu was surprised to hear Major Loki's voice emanating from the remains of its armor, praising Yuu for his victory. After Loki gave Yuu some information about Hreidmar, he declared to him that he would do whatever it was necessary to prevent an increase in Dragons, prompting Yuu to rush back to the villa. Upon arriving at the destroyed building, Yuu was relieved to see that everyone was fine, but was shocked when he saw that Iris' body was exhibiting signs of Dragon transformation.

Following the destruction of the villa, Yuu and company relocated to a volcanic crater lake in order to plan their operation against Kraken Zwei. Taking advantage of the fact that everyone was away, Yuu approached Vritra and pleaded with her to tell him what she knew about Iris' condition. Eventually, Vritra relented, informing Yuu that Iris' body was turning into that of a Dragon as a result of her having inherited Basilisk's Authority, much to Yuu's shock. After helping Vritra wash her face and heading back, Yuu chanced upon a naked Jeanne and was surprised to find out that she was actually a girl. Although Jeanne was fearful of his reaction to this, Yuu assured her that their relationship wouldn't change, prompting Jeanne to burst into tears and embrace him.

Upon receiving information that Kraken Zwei was approaching at a faster rate, the Dragon Subjugation Squad put their operation in action. While Iris, Lisa, Firill and Tear stood by, ready to attack the hybrid, Yuu joined Jeanne and Haruka in waiting for Kraken Zwei's approach. Although the hybrid came to their location and seemed open to persuasion, it turned out that it merely wished to mark Yuu as a mate. After Yuu rejected her, Kraken Zwei turned hostile and started attacking them. Despite Yuu's plea for Haruka to order the Dragon Subjugation Squad to attack, she refused to do so and continued attempting to reason with her. When Zwei came close to killing Yuu, he was pushed aside by Haruka, who took the blow in his place. Yuu immediately ordered the Dragon Subjugation Squad to attack and held Haruka in his arms as she seemingly died.

V8 I7

Yuu marks Iris and Zwei

Following the Dragon Subjugation Squad's failure to destroy Zwei, Yuu engaged her himself, using his Fafnir to apparently kill her. However, due to the fact that Zwei was closer to a Dragon than a human, Yuu's attempt to kill her was unsuccessful, leading to his incapacitation at the hands of the hybrid. However, before Zwei could kill him, she was interrupted by the arrival of a further dragonified Iris, who engaged Zwei. Despite her enhanced Catastrophe, however, Iris was also defeated by Zwei, with the hybrid attempting to mark her. At that moment, Yuu's true nature as a Dragon awoke out of a desire not to lose Iris, allowing him to mark both her and Kraken Zwei as his mates, before passing out after grabbing Iris' hand. After regaining consciousness, Yuu noticed that Iris had been restored to her normal appearance, while Kraken Zwei had assumed the form of an ordinary young girl as a result of transforming into the same kind as him. Upon witnessing Zwei crying in Jeanne’s embrace, Yuu fainted again. Following the conclusion of the battle, Yuu awoke in a helicopter bound to Midgard and was very surprised to see that Haruka was still alive as a result of having received Charlotte’s blood in the past. Upon meeting the rest of the girls, Yuu was shocked to find out that he had also marked the entire Brynhildr Class and Kili as his mates.

Cerulean EngageEdit

In Volume 9, Yuu awoke from his nightmare to find himself in Charlotte's room, where he had been confined for the past three days due to his marking of Brynhildr Class as mates. After greeting Charlotte with her nickname at her insistence, he bore witness to the squabble between Charlotte and Mica, which ended with Charlotte being forced to return to work. He was then relieved to hear from Mica that everyone was doing well and that Kili and Kraken Zwei were behaving. The following day, Yuu received a visit from Iris, but was greatly embarrassed when she requested to take a bath with him. However, he was concerned when he heard that Tear was behaving abnormally, resolving to find a way to speak with her. At that moment, Charlotte intruded in the bath and, after joining them as well, warned Yuu that he was not to leave this room under any circumstances, explaining to him that it was possible he was a humanoid Dragon and the dangers that could befall the girls if they chose to transform into the same kind as him. After accidentally seeing Charlotte and Iris' naked bodies, Yuu passed out from the stimulation.

That evening, Yuu contacted his classmates in order to find out about Tear's condition, becoming concerned when Kili informed him that Tear was in low spirits and was seen discussing with Vritra. He became even more worried when Ren hinted that something was up with Ariella as well. The next day, Yuu was brought to an underground training room in order to meet with Zwei. After seeing that Zwei was refusing to accept the name Shion, Yuu attempted to persuade her, but was surprised when she called him Papa. Jeanne proceeded to explain to him that she had told her he was her father in order to justify the connection Zwei felt towards Yuu. Thanks to Yuu's words, Shion accepted her name, although he was embarrassed when Mica teased him about having obtained a wife and a daughter. At the same night, Yuu was contacted by Major Loki and was shocked to hear that the world was sliding back into a state of war due to the disappearance of Dragons, humanity's common foe. When Loki asked him to take out Charlotte, Yuu vehemently objected, but at that moment, communications were cut off by Charlotte. When she asked him if he would follow Loki's orders and take her out, Yuu resolutely stated that he wouldn't, but was surprised when Charlotte stated that Loki might be justified in his view of her being the worst Dragon for mankind.

V9 I5

Yuu escorts Mitsuki after turning her into his kind

During NIFL's attempt to invade Midgard under the pretext of an inspection, Yuu was informed of the situation by Mica, who proceeded to escort him to Charlotte's underground cottage, while also explaining to him that the marked Ds would decide by themselves whether they wanted to become his kind or not. Upon settling down, Yuu, Iris and Jeanne discovered a photo of Charlotte and her father, with Yuu and Jeanne being shocked at his resemblance to Major Loki. At that moment, Mitsuki came in, having won the right to become the first person to discuss things with Yuu, and asked him to take a bath with her in the hot spring, much to his embarrassment. When Mitsuki voiced her worries that Yuu might be burdened by his responsibilities, Yuu assured her that he was willing to face any problem for her sake, prompting Mitsuki to request for him to change her by means of a kiss on her dragon mark, much to Yuu's embarrassment. After returning from the hot spring, it was decided that Firill, Lisa and Ren would be the ones to discuss with him the next day. However, at that night, while Yuu was having a nightmare about the accident that had killed Mitsuki's parents, he was suddenly awakened by Kili, who kissed him in the lips in order to undergo the dragon transformation after a brief discussion. Although Yuu asked her to leave, Kili attempted to take things further by seducing him and asking him to make a baby with her, but was interrupted by Ariella's arrival. Yuu thanked her and apologized, but was concerned with Ariella's response.

The following day, thanks to his discussions with Firill, Lisa and Ren, Yuu realized that he selected everyone as mates because he cared for them and did not wish to lose them, and because they liked him as well. He also realized that the problem of them having to be confined in Midgard could be solved by simply changing the rules as Albert Crest had done for the Ds. He also promised Ren that he would definitely persuade Ariella to become the same kind as him. However, at that moment, the cavern shook greatly as a result of NIFL using the Main Cannon Babel Replica to destroy Midgardsormr's final defensive line. In light of this new development, it was decided that Yuu, Kili, Jeanne and Ariella would take turns watching the two entrances for signs of enemy intrusion. During his shift, Yuu was approached by Tear and Vritra, with Tear asking him to hold hands and Yuu promising to protect her, no matter what troubled her. After her transformation was complete, Tear started explaining everything about Counterdragons and True Dragons to Yuu, before Vritra took over, expressing her opinion that Yuu couldn't be Neun, the ninth Counterdragon, since the world was no longer able to produce Counterdragons capable of warding off the approaching ninth calamity. Vritra also stated that if Yuu was Neun, he should have already encountered the Ninth True Dragon and asked him when exactly he realized he was not human. As Yuu's mind flashed back to the accident that killed Mitsuki's parents, Ren came running, yelling that she couldn't find Ariella anywhere.

V9 I10

Yuu prepares to head out in order to rescue Ariella

Yuu proceeded to rush to Ariella's location and found her standing guard. After confronting her about her disappearance and asking her to become his mate, Yuu was shocked to hear that Ariella was working as a spy for NIFL and intended to kill Charlotte, while also being surprised that Ariella's murderous intent was similar to his Fafnir. Despite that, Yuu stated that he was willing to forgive her for everything, even after hearing that she had brought in the NIFL troops during the Leviathan incident, stating that he would stop her no matter what. He then engaged Ariella in battle, which was interrupted when she brought down the ceiling of the cavern, separating them. However, Yuu used Ether Wind in order to transmit his feelings to the retreating Ariella, declaring that he would never give up on her. He then joined everyone in the cottage, explained the situation and asked for their help in stopping NIFL and rescuing Ariella.

Invisible SuccessorEdit

V10 C1

Yuu promises to Iris that he will not kill anyone

In Volume 10, Yuu and company made their way to Charlotte's office in order to protect her from NIFL's invading forces. While discussing with Iris about his tendency to run off ahead on his own and the changes in Iris' ability to use Catastrophe, Yuu was surprised when she pointed out to him that he should avoid killing people, promising to her that he would refrain from doing so. Upon noticing Kili's dissatisfaction at Tear being close to Lisa, Yuu confronted her about this, questioning her on the reason she killed Tear's parents and becoming angry at Kili's dismissive attitude. However, he was shocked when Kili informed him that Tear's parents meant to sell her off and that she had saved her. After hearing that, Yuu encouraged Kili to try and get closer to Tear.

V10 I5

Yuu pats Charlotte

Upon arriving at Charlotte's office, Yuu was shocked to see that she had been stabbed, but calmed down once Charlotte explained that she had done this herself to collect blood. After explaining the situation regarding Ariella, Yuu, in response to Charlotte's query, resolutely declared to her that he would protect her as a friend and stop her if she were to make a wrong decision. Following Charlotte's explanation of her plan of action and the girls' declaration that they did not fear her, Yuu asked to speak with her privately. When the two of them were left alone, Yuu questioned her about the reason NIFL and Ariella wished to eliminate her, while also bringing up the fact that Major Loki and her father had identical appearances. In response, Charlotte revealed that Loki was a descendant of her father's older brother, who had been bestowed with an Authority designed to exterminate mankind, but did not use it for his entire life, leading to it being labelled as Code Lost. She also revealed that Loki's father also possessed Code Lost and had murdered her family under NIFL's orders, but she refused to elaborate on why she was regarded as a threat. Yuu thanked her and proceeded to pat her head upon her request, expressing his admiration for her hard work. At that moment, they were notified that hostile forces were approaching, so Yuu prepared to head out. Before leaving, Charlotte informed him that the first possessor of Code Lost was named 'Colorless' Fafnir.

V10 I6

Yuu embraces Ariella

After leaving Vritra, Shion and Jeanne in Charlotte's office, Yuu prepared to confront the approaching Ariella alongside Ren, Iris, Mitsuki, Kili and Tear. Upon explaining his plan to everyone and assigning positions, Yuu headed to the front alongside Kili. Shortly afterwards, they were attacked by Sleipnir, led by Ariella, and were thrust into a difficult battle due to Sleipnir's abnormal abilities. However, thanks to Yuu's newfound power to share feelings and thoughts with his mates, he was able to approach Ariella and turn her into his own kind after touching her. As a result of using Ether Wind at that time, Yuu also gained access to Ariella's memories, realizing that everything she had done was for the sake of the children she had befriended while in the dragon-hating organization. He then confronted her inside her mindscape, with Ariella hinting that Charlotte's Authority was something very dangerous if unleashed fully, which was why she wished to stop her. After returning to his senses, Yuu comforted the crying Ariella by embracing her and later on returned her ribbon to her. When Ariella questioned his decision to protect the principal, Yuu stated that if Charlotte were to make a wrong choice, he would stop her as a friend without resorting to killing her. After the topic shifted to Ariella's feminine charm, Yuu assured her that her legs were very attractive, which prompted her to shout at him in a fluster. While restraining Sleipnir, Yuu questioned Ariella on their strange behavior earlier, with Ariella revealing that everyone had ingested a capsule that had enhanced the potency of Code Lost and had allowed them to perfectly synchronize.

V10 I8

Yuu kills Loki

Following the conclusion of the battle against Ariella, Yuu and company headed to the surface and were surprised to see that the whole island had been covered by a red mist that had rendered everyone unconscious. Shortly afterwards, Yuu came across Mica, who informed him that the mist was a result of Charlotte losing control of her powers and that Yuu and company were unaffected for the time being due to being closer to Dragons than humans. After hearing an explosion coming from the front gate, Yuu urged everyone to go and investigate, but not before reaffirming his decision to protect Charlotte to Ariella. Upon reaching the front gate, Yuu was very surprised to see Major Loki present, accompanied by two Hreidmars. After one of the Hreidmars was killed due to an unmanned weapon's mysterious detonation, Yuu approached Loki, asking the girls to stay back. Loki proceeded to explain the true nature of Charlotte's Authority, how the Hreidmars came into being and how he transferred Code Lost into Yuu by killing holders of the scrapped factor with poison mixed with his blood. Loki then revealed that he also currently possessed Code Lost by having killed all remaining successors and having inherited Sleipnir’s factor. He then proceeded to demonstrate Code Lost's power of killing people through imagination alone by eliminating the last Hreidmar. Following Loki's declaration of his intent to kill the girls, Yuu yelled for everyone to run away and engaged him in combat. However, due to the fact that Loki's ability to interfere with causality was higher than his, Yuu was completely outmatched, suffering several injuries while being unable to retaliate. When Loki declared that the girls' deaths had been sealed, Yuu charged at him in anger, but was shot through the chest by Loki. While Yuu was half-conscious, Loki revealed that he had lied about the girls dying. Upon realizing that he was still alive due to Hraesvelgr's Authority residing in his heart, Yuu fully activated it and stood up enveloped in Ether Wind, piercing through Loki with his hand. With his dying breath, Loki revealed to Yuu that with his death, Yuu would inherit the complete Code Lost and would kill every person he knew due to his inability to control the fully activated Authority, much to Yuu's horror.

V10 C2

Yuu and Charlotte struggle to control their Authorities

Struggling to keep Code Lost under control, Yuu made his way to the clock tower, asking Charlotte to control his mind, while Charlotte asked him to kill her. After the two of them engaged in idle banter, Yuu realized that their Authorities were currently counteracting one another. At that moment, Vritra approached Yuu and, after grudgingly admitting that he might be Neun since he didn't dragonify even after fully manifesting Hraesvelgr's Authority, suggested that Yuu split Code Lost between his recently arrived mates. Although Charlotte requested for Yuu to kill her before going through with this, Yuu refused, stating that there was another way. Following the success of the transfer, Yuu borrowed dark matter from the entire Brynhildr Class to form a new Anti-Dragon Armament with blueprints bestowed to him by Tear, the Hyperspace reversion rocket-assisted artillery, Abyss, which erased all traces of Charlotte's blood mist. Subsequently, Ariella's successful attempt to protect everyone from Babel Replica's blast and Tear's destruction of the superweapon brought this incident to a close. In the aftermath of the battle, Yuu took a bath with Ariella upon Ren's insistence, while also thinking that it was fortunate that Major Loki was healed by Kili. Upon Ariella's request, Yuu touched her dragon mark while in the shower. However, the tender atmosphere was interrupted by Kili's arrival and the insistence of Charlotte, Shion, Jeanne and Tear to join in the bath as well, with Yuu resolving himself to weather the incoming chaos.

Prismatic GardenEdit

In Volume 11, Yuu moved back to Mitsuki's dorm alongside the rest of his friends, thanking Charlotte for everything. During the move process, he was tasked with helping Firill pack her large amount of books. When Firill announced her intent to reward him for his assistances, Yuu was embarrassed, but was afterwards confused when Firill warned him that his troubles were just beginning. He soon came to realize what she meant when the girls started quarreling about who would get the room next to his. Eventually, it was decided that everyone should participate in a game to settle this. Yuu also took part, although he was quickly eliminated, while also feeling perplexed about Vritra's strange behavior towards him. At that night, Yuu was visited in his room by Vritra. Although confused by her antics, he came to the conclusion that she wished for them to get along better and agreed to have a heart-to-heart talk with her about the Ninth True Dragon and his own Authority. At that moment, Mitsuki entered the room, forcing Yuu to hide Vritra under his sheets. When Mitsuki informed him that she had been using the room in his absence and indirectly asked for permission to still use this room, Yuu was surprised, but allowed it. After Mitsuki left, Vritra did so too, asking Yuu to treasure his sister.

V11 I4

Yuu declares that Jeanne is under his protection

The following day, Yuu watched the introduction of Kili, Vritra, Jeanne and Shion to the rest of the school assembly, feeling somewhat disheartened with cross-dressing Jeanne's popularity with the rest of the students compared to him. After the four of them were placed in Brynhildr Class, Yuu and the rest were forced to deal with the rest of the students' obsession with Jeanne. A few days later, Yuu was visited by Jeanne, who was torn about whether she should wear a female uniform. Yuu encouraged her by stating that she would look very attractive in it, convincing her to try it on. However, she accidentally tackled him into the bed due to her embarrassment, but this didn't stop Yuu from looking at her and declaring that she was indeed pretty. When Jeanne asked Yuu to punish her for her inappropriate behavior, he accidentally touched her bottom, passing it off as her punishment. The next day, due to Jeanne's misleading words about the previous night, Yuu was sentenced to write even more repentance essays. Upon seeing that the girls were not giving up their pursuit of Jeanne, Yuu decided to take matters into his own hands and declare that Jeanne was under his protection and thus off-limits. Although this did get the rest of the students to back off, it also resulted in them starting to ship Yuu with the cross-dressing Jeanne.

After Charlotte announced her intent to hold a festival and Shion expressed interest in participating, Yuu and the rest of the class decided to help out with Haruka's yakisoba stall. As such, it was decided they would have a barbecue party in order to learn how to prepare yakisoba. During the barbecue, due to a misunderstanding arising from his conversation with Shion, everyone was convinced Yuu had a fetish for breasts. Following Haruka's lesson on how to make yakisoba, Yuu was approached by Charlotte, who informed him that the world leaders had withdrawn their demands for her to use her Authority, but had confined her in Midgard. Seeing that she felt down about being unable to prevent wars from occurring, Yuu encouraged her by stating that Major Loki had surely seen to it and that she should simply watch over the world. After calling himself her best friend, Yuu was shocked when Charlotte offered to let him play with her breasts as a reward for his assistance during Midgard's invasion. However, at that moment, she was blown away by Iris' explosion, who misunderstood the situation. After helping her dig out Charlotte, Yuu was caught off guard when Iris buried his face in her bosom, asking him to be satisfied with this and stop staring at other people’s chests. While walking away, Yuu chanced upon Mitsuki, who had witnessed this scene. Although he was nervous, Mitsuki assured him that she wasn't mad, but asked him to decide what sort of position she occupied in his heart. Upon hearing that, Yuu promised to give her an answer during the school festival.

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Yuu accompanies Tear during the festival

On the day of the festival, Yuu was in charge of preparation alongside Lisa, praising her beauty. After his shift was over, he accompanied Kili, Vritra, Ariella and Ren to a ring-tossing game, where the winning pair would get to monopolize him. Yuu also participated in the game, winning a bunny for Ren, a bag of candies for Vritra and a brooch for Tear. Seeing that Kili and Ariella were equal in skill and that their competition wouldn't conclude any time soon, Yuu took Ren and Vritra to check the nearby stalls. Afterwards, Yuu participated in goldfish scooping alongside Iris, Tear, Firill and Jeanne. Upon finding himself alone with Tear, Yuu gave her the brooch, although she insisted that he put it on her, and reassured her that even if the ninth calamity was approaching, she was allowed to have fun on this day. When the sun set, Yuu met up with Mitsuki, who proceeded to express her love for him. Yuu, in turn, declared that, while he cherished everyone, the one dearest to him was Mitsuki. At that moment, however, the Ninth True Dragon started manifesting due to Mitsuki's emotional turmoil, much to Yuu's alarm. When Vritra showed up and explained the nature of this darkness, along with the fact that he had sealed it inside Mitsuki and that she would be consumed by it, Yuu ignored her warnings and rushed to Mitsuki, using his Authority to suppress the ninth calamity. However, the End Matter that had spread out of Mitsuki took the form of her deceased parents, forcing Yuu to use Fafnir to eliminate it. Although momentarily relieved, Yuu was shocked when Vritra stated that his desire to protect Mitsuki stemmed from his instincts as a Counterdragon, thus calling his feelings for her into question.

Darkness Disaster Edit

In Volume 12, following the incident on the beach, Yuu revealed to the rest of Brynhildr Class, Mica and Haruka his status as the Ninth Counterdragon and the fact that the Ninth True Dragon was lurking within Mitsuki. After everyone agreed to keep an eye on Mitsuki alongside Yuu in shifts, Yuu was left alone with Iris after the rest excused themselves. Although reluctant at first, he eventually shared with Iris the fact that, while he considered Mitsuki to be the one dearest to him, it was possible that those feelings originated from his instinct as a Counterdragon, stating that he would find the answer eventually. While having a discussion with Ariella later on, Yuu received an urgent call from Charlotte, informing them that a number of unknown territories had appeared around the world along with a mysterious dragon-shaped lifeform, whom Tear identified as the Fifth True Dragon, 'Eternal Longevity' Bahamut. Upon being informed that NIFL had requested their cooperation to deal with it due to Iris' Catastrophe, which could defeat Bahamut, Yuu and the rest agreed to head out. When the problem of transport came up, Yuu was surprised when Tear stated that they simply had to complete Marduk.

Following the revelation that Marduk was in fact a giant battleship, Yuu borrowed dark matter from every D in Midgard while Tear transmitted the complete blueprints to his mind, succeeding in materializing the enormous ship. Although assaulted by a splitting headache due to the strain placed on his mind by the mental link with Marduk, Yuu ignored it. After boarding Marduk and bidding everyone else farewell, Yuu and the rest of Brynhildr Class alongside Haruka set off. Upon assigning cabins to everyone, Yuu chose to remain on the bridge to direct Marduk, but accidentally received live feed of what happened inside the cabins due to his errand thoughts. When Tear discovered him, she asked Yuu to join her in the bath as 'punishment'. While washing her hair, Yuu was informed by Tear that she had been unable to find any information about the seventh calamity due to the fact that Kiskanu's plant network had been destroyed to such an extent that no recording or analysis was possible. As Yuu comforted Tear and the two shared a moment, Marduk suddenly began malfunctioning. Upon discovering that someone had hacked its systems, Yuu and Tear rushed to the bridge while Tear neutralized the invader, who was revealed to be Atla, the machine intellect which once governed Atlantis, by Major Loki. After he explained her origins and urged her to share the proper way to control Marduk, Yuu assigned Jeanne as his co-pilot following Loki and Atla's advice. Upon receiving information from NIFL through Marduk's system, Jeanne informed Yuu about the state of the unknown territories, the true nature of Bahamut as an organism which consumed heat and the fact that it was leaving a trail of darkness behind it.

Shortly before the operation against Bahamut, Yuu took his position on the deck alongside Iris and Kili, with the three commenting on the fact that Bahamut had chosen the Earth instead of the Sun to absorb energy from, speculating that something on the planet attracted the True Dragons. Upon making contact with Bahamut, Iris attempted to eliminate it with her Catastrophe, but failed due to insufficient output, forcing Yuu to issue a retreat order after intercepting Bahamut's counterattack. In order to figure out a way to destroy Bahamut before their second confrontation with it, Yuu had a discussion with Vritra, Mitsuki and Iris to brainstorm ideas. After sharing his experience when he temporarily obtained full access to Hraesvelgr's Authority, the conclusion was that Iris had to discover the location of her Authority and temporarily turn into a Dragon in order to use its full power.

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Yuu kisses Firill's hand

While passing above the Principality of Erlia, Yuu joined Firill at the deck as they reminisced about their past experiences there. Yuu was surprised when Firill suddenly asked him to kneel and kiss the back of her hand, but complied with her request. However, he was informed by Firill that they had just performed a simplified marriage ceremony much to his shock. Just as he was wavering over what to do, Firill stated that this marriage was only effective within the Principality's borders, leaving Yuu with a mixed feeling of relief and regret at the same time. Upon arriving at the second defense line, Yuu had a brief discussion with Major Loki, where he expressed his opinion that their mutual survival during Midgard's invasion was partly due to Atla's hesitation to fire the Babel Replica, much to Loki's surprise. While preparing for the operation against Bahamut, Yuu was put in a tight spot when everyone started questioning Firill's close proximity to him, forcing him to make up an excuse on the spot.

During the second battle against Bahamut, Yuu neutralized its attacks and inflicted damage on it by using Marduk's armaments while the rest of Brynhildr Class supported him with their own attacks. However, Iris' enhanced Catastrophe was blocked by the Sixth True Dragon, 'Anomalous Dawn' Nyarlathotep, who suddenly appeared on the battlefield. Although Mitsuki requested for Yuu to let her fight since Kraken's Authority would be effective against Nyarlathotep, he instead asked Shion to come to the deck after she insisted that her Authority was stronger. Thanks to her antimatter shot, Nyarlathotep was destroyed, giving Iris a clear shot at Bahamut and enabling her to eradicate it with her Catastrophe. However, before they could celebrate, the darkness extending from Bahamut's trail engulfed Marduk. Yuu's attempt to resist it through Code Neun proved to be futile until Mitsuki absorbed all of it, revealing that she had mastered the Authority. Following the conclusion of the battle, Yuu was approached by Vritra, who hesitantly suggested that a way to destroy the Ninth True Dragon was for Yuu to have Mitsuki to seal the entirety of the ninth calamity's End Matter within her and then kill her through Code Lost, leading to Yuu's angry outburst. Their argument was interrupted by the sound of an explosion, with Jeanne reporting that Marduk had been damaged. At that moment, Mitsuki appeared, stating that she had caused the explosions, much to Yuu's shock. After Mitsuki announced her intention to take care of the remaining territories and stated that she would have help from the Ninth True Dragon, which had assumed Miyako's form, Yuu attempted to prevent her from leaving, but was distracted when she mentioned that Iris was in her cabin and in need of help. As such, Yuu could only watch powerlessly as Mitsuki bid him farewell and disappeared.

Powers and AbilitiesEdit

Dark Matter Generation: Like all Ds, Yuu has the ability to generate and manipulate Dark Matter, transmuting it into various forms. However, unlike most Ds who can generate at least 10 tons of Dark Matter, Yuu can only materialize up to 10 kilograms after conversion. Yuu is especially proficient at constructing complex objects such as guns visually, which is considered impossible for average Ds. That is because Yuu has a clear image of what he wants to construct due to having detailed blueprints of weapons downloaded into his mind by Yggdrasil.

  • Siegfried: Yuu's Fictional Armament, which takes the form of a large-caliber ornamental gun. It is capable of firing Dark Matter as bullets, which Yuu transmutes into any matter and shape he wishes. However, Siegfried is only able to fire 3 bullets before losing its shape and needing to be re-constructed again due to Yuu's low dark matter capacity.
    • Plasma Bullet: A bullet made of plasmafied compressed air. It has enough power to pierce through diamond with ease.
    • Air Bullet: Yuu fires a bullet of air that can be used to push himself further up into the sky.
      • Air Pressure Bullet: Yuu fires an Air Bullet at a higher pressure, creating an explosion of air perfect for cushioning impacts.
    • Cage Bullet: Yuu fires dark matter that is transmuted into a small metal cage to trap his target.
    • Red Bullet: Using what little amount of dark matter is left in Siegfried, Yuu transmutes it into a high-temperature blade of air by compressing air into the shape of a knife.
    • Smoke Bullet: Yuu transmutes dark matter into smoke. This is mostly used for smokescreens and to dissipate Dark Matter generated by an opposing D.
    • Nitro Bullet: Creates a large volume of nitrogen to produce a gust of wind that can blow away fire.

Anti-Gravity: Upon defeating Leviathan, Yuu inherited its Authority, Code Vier. This enables him to generate repulsive fields that can negate gravity and reflect incoming attacks by converting his dark matter into anti-gravitational matter. Yuu can also apply these capabilities into bullets of the weapons he creates. However, he is unable to bring out power on the level of Leviathan.

  • Half Gravity: An alternate form of Anti-gravity, in which Yuu fires a bullet that halves the weight of the target.
  • Gravity Zero: A variation of Anti-gravity, which temporarily disables gravity in a certain area.
  • Gravity Grave: Another variation of Anti-gravity that uses two repulsive fields to distort space and shoot it as a projectile.

Ether Wind: After defeating Hraesvelgr, Yuu inherited its Authority, Code Drei. This enables him to generate golden particles that are able to manifest the souls of sentient organisms and can also be used to immobilize living beings by transmuting his dark matter into Ether Wind. He is also able to hear the thoughts of other people and even enter the depths of their consciousness by using Ether Wind. Yuu can also fire these particles through the weapons he creates. However, just like with anti-gravity, Yuu is unable to bring out power on the level of Hraesvelgr. In Volume 10, though, Yuu was able to fully utilize Ether Wind after nearly being killed by Loki by materializing his spirit to envelop his body and allowing him to move his body using his mind only. In this state, Yuu becomes impervious to any form of physical interference and his reaction time and reflexes are heightened since the process of transmitting orders from the brain to the muscles is skipped. In Volume 13 Yuu shows the ability to form weapons using Ether Wind much like a Fictional Armament.

Code Neun: Yuu's Authority as a Counterdragon. Although not much is known about the true nature of this Authority, it's confirmed that it is capable of temporarily sealing the Ninth True Dragon inside a human being, in this case, Mitsuki, as well as restoring the original form of those consumed by the ninth calamity's darkness. It's also capable of warding off End Matter, a substance that the Ninth True Dragon is composed of and is diametrically opposed to Dark Matter.

Code Lost: A part of the scrapped Authority of 'Colorless' Fafnir, which was implanted into Yuu by Loki Jotunheim by using Yuu's blood mixed with poison in order to kill other holders of the scrapped factors. Code Lost can be further strengthened by absorbing more factors from other holders. It also enabled him to neutralize the effects of its counterpart, Code Acht. However, due to the fact that Yuu was unable to control the Authority's killing intent towards humanity, he was forced to split it between most of his mates.

  • Fafnir: An alternate persona which takes control of Yuu's body whenever he exhibits killing intent. In this state, Yuu's physical abilities and perception are enhanced to superhuman levels, allowing him to move and react at instantaneous speeds, especially against hundreds of projectiles. However, the opponent must be human (or in the form of a human in the case of Vritra), Fafnir will pick the simplest and most efficient way to kill them without fail. It's revealed in Volume 11 that, due to Yuu possessing a greater amount of Code Lost than before, Fafnir is currently stronger than it originally was.
  • Causality Manipulation: When Yuu inherited the complete Authority in Volume 10, it enabled him to kill anyone simply by imagining the manner of their death or just their faces. It's mentioned by Loki that this is because Yuu has experienced the feeling of 'true' killing intent. Even after splitting the Authority between his mates, Yuu has retained this ability as was shown in Volume 11, when he used Fafnir to kill a part of the Ninth True Dragon, which had assumed human form.

Marking: In Volume 8, Yuu discovered that, as a Counterdragon, he had the ability to mark multiple Ds as his mates and transform them into the same kind as him upon contact.

  • Telepathy: In Volume 10, Yuu displayed the ability to sense the thoughts and feelings of those he has marked as his mates even over a great distance.

Combat Training: Yuu has received three years of intense physical and mental training under NIFL in order to become the world's strongest assassin.

  • Expert Marksmanship: Yuu is naturally adept at using firearms, his main weapon of choice, due to his training at NIFL.
  • Hand-to-hand Combatant: As a former member of NIFL, Yuu is adept at close-quarters combat.
  • Enhanced Senses: His time at NIFL has also enhanced Yuu's senses to the point where he was shown to be able to detect the number of people in his surroundings as well as discern their physique from the sound of their steps.
    • Threat Detection: Yuu is capable of sensing danger around him, such as killing intent from others, even from outside his field of vision and at far distances.
  • Peak Human Reflexes: Along with being an excellent fighter, Yuu has extremely high reaction speed, making him capable of maneuvering around incoming attacks as well as catching them.

Weapon BlueprintsEdit

After making a deal with Yggdrasil, Yuu was able to obtain blueprints of weapons belonging to the lost civilization of Atlantis by having them downloaded directly into his mind. However, each time Yuu makes a download for additional information, it not only gives him a massive headache, but Yggdrasil also blocks a part of his memories. This problem was rectified when Tear became the new core of Yggdrasil and restored his memories.

  • Anti-Personnel Weapons: Weapons that are primarily used to incapacitate humans.
    • AT Nergal: An electroshock gun that is used to stun his opponents. This is Yuu's main weapon of choice against ordinary humans.
    • Enlil: Anti-armor weapon which fires a high vibration bullet to penetrate through thick armor.
  • Anti-Materiel Weapons: Weapons that are designed for use against military equipment.
    • AT Ishtar: Anti-materiel sniper rifle.
  • Anti-Army Armaments:
    • AT Baal: A weapon from in the form of a gunblade for both close and mid range combat, whose cutting edge is one with the barrel.
  • Defensive Armaments:
    • Uruk 73E: Anti-explosive armament in the form of a large shield.
    • Damascus 09P: Anti-material armor in the form of small plates. Used for pinpoint defense.

Anti-Dragon Armament, Marduk: A series of weapons used mainly for anti-Dragon combat and manipulated through a mental link. However, due to the massive amount of memories taken from him, Yuu tends to sever his link with Yggdrasil before finishing the download of their blueprints, leaving most of these weapons in an incomplete state (although, according to Yuu, their power is not enough to defeat Dragons even in their complete state). Due to being incomplete, these weapons eventually malfunction and self-destruct after use. The weapons also require a substantial amount of space and secure footholds to be used effectively due to their enormous size. In order to construct anti-Dragon armaments, Yuu must borrow dark matter from another D due to his low capacity and the enormity of the weapons. Another downside is that using these armaments completely drains Yuu, leaving him unconscious for a while. According to Atla, pilots that have mental links with Marduk are called linkers.

  • Deus Dragon, Marduk: Described as the second calamity's ultimate trump card, Marduk's true form is revealed to be a massive battleship roughly two hundred meters in length. The ship's body is covered with silver-white armor with grooves, tracing out a network of geometric patterns reminiscent of pulsating blood vessels, brightening and dimming in periodic cycles. Furthermore, all the other anti-Dragon armaments that were previously summoned by Yuu are mounted throughout Marduk's body. The ship is capable of flight even in space by using the variable-sweep wings on the sides as gravitational control devices. Yuu is connected to the ship via mental link, which provides him with a full grasp of the entire ship's capabilities and absolute control over it. However, the strain of manipulating such a massive and complex weapon causes intense headaches to him. Yuu first summoned the complete form of Marduk in Volume 12 after Tear supplied him with the remaining data through her connection to the Akashic Record, while every D on Midgard continuously supplied him with enough Dark matter to materialize it due to its enormous size. According to Atla, Marduk requires at least two linkers to control safely.
    • Megiddo in Anime
    • Megiddo in Manga
    • Special Artillery, Megiddo: A large cannon that fires a bullet of blue-white light, causing everything caught in its blast to disintegrate on the atomic level. Megiddo is even able to reach the dimension where the true body of Vritra lives and inflict damage on it. It was first used by Yuu during Hekatonkheir's attack on Nanato City, although its full name was revealed in Volume 2. After completion, the Marduk battleship contains a total of two Megiddo cannons.
      • Babel in Anime
      • Babel in Manga
    • Main Cannon, Babel: A giant cannon with a split barrel and a lens-like device in the middle. Babel fires a super-gravitational singularity in the form of a black torrent that tears space to crush everything existing within the range of its attack. It was first used by Yuu in Volume 1 to counter Leviathan's Anti-gravity. As the main cannon, in its complete form, Babel protrudes from the prow of the Marduk battleship.
    • Psionic multi-barreled cannon, Noah: A double-barreled artillery on a rotating turret. Noah is a weapon designed for amplifying and firing the gunner's thoughts, causing a slight amount of ether particles to materialize under the influence of the compressed mental waves, thereby obtaining the power to interact physically with them. Other people can also transfer their thoughts to the gunner by utilizing the same principle as dark matter transfer, thus increasing Noah's power. Unlike other anti-dragon armaments, this weapon was in an almost complete state upon materialization due to its small size, allowing multiple copies of it to be constructed. Yuu used it for the first time in Volume 4 to defeat Hraesvelgr. Upon completion, the Marduk battleship contains a total of eight Noah multi-barreled turrets.
    • Hyperspace Reversion Rocket-assisted artillery, Abyss: A gigantic missile pod in the shape of a rectangular box, which contains a large number of missiles. Abyss is a disintegration weapon that forcibly creates hyperspace that is not supposed to exist at the same spatial coordinates, thereby causing the world's corrective force to erase everything at those points together with the surroundings. Due to its sheer size, it requires dark matter from several Ds in order to materialize it. Yuu used it for the first time in Volume 10 after receiving data on its specs from Tear, who was connected to the Akashic Record, in order to eliminate all traces of Charlotte's blood mist from Midgard. In the completed Marduk battleship, the missile pods of Abyss are located behind the bridge.
    • Light Shell Barrier, Eden: A shield of light created by multiple small units. The configuration of the barrier can be changed to either surround the entire ship or protect specific parts. There are restrictions on the number of times it can be used and its active duration, but its defensive power, when combined with multiple wind barriers created by Ds, is strong enough to completely block 'Eternal Longevity' Bahamut's attacks.


Yuu Mononobe/Relationships


Yuu Mononobe/Image Gallery


  • Siegfried is the name of the main hero from The Song of the Nibelungs, an old German epic poem.
  • Most of the ancient weapons Yuu creates seem to be named after Mesopotamian deities and cities.
  • His Fictional Armament was designed and named by Mitsuki.
  • AT Nergal and AT Ishtar were mass produced by NIFL and are used as their main weapons.
  • Many of the newest NIFL weapons are inspired by design ideas Yuu secretly passed to his friend in NIFL's weapon research department, which are based on the mental blueprints obtained from Yggdrasil.
  • A running gag in the series is Yuu's tendency to find himself in various erotic situations, despite the fact that he doesn't actively seek them.


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