Owari no Seraph Wiki
Owari no Seraph Wiki

Gekkouin (月光韻 Gekkōin?, lit. "Moonlight Rhyme"), birth name Gekkouin (ゲッコーイン Gekkōin?), is a high-ranked manifestation-type demon of the Black Demon Series. He formed a contract with Yoichi Saotome and became his Cursed Gear.


Gekkouin's weapon takes the form of a big black bow with glowing eye-like parts at the upper and lower curves of the bow. He manifests as a black and green intangible and amorphous flame-like bird demon.

In Yoichi's mind, Gekkouin often appears as Yoichi's deceased older sister, Tomoe. While Gekkouin is possessing Yoichi, his body sprouts two short horns on top of his head, develops fangs, sharp dark nails, and has abnormal eyes.

His real form is a well-built, young man with tousled light hair and a pair of curved horns sprouting from his head. His pointed ears and fangs reveals that he was once a vampire. He wears a long, black coat that has the front open to reveal his body, along with matching pants and boots. On his left arm, he dons a sort of spaulder that reaches down midway of his arm. Additionally, he also wears black, finger-less gloves. The left side of his face is covered with a black, curse-like mark.[1] Within a dream like world when Gekkouin is injured he bleeds.


Gekkouin hates weak-willed individuals and initially could not stand the pure hearted Yoichi. Someone having a gentle soul, being kind and having a great love for others are all qualities that he despises. Later on, they apparently become friends, as Yoichi states they chat in his dreams. Considering a matter, if something unexpected is something Sika Madu did not foresee then Gekkouin is determined to fight at full strength being unable to afford to fail. Easy going in general, even when battling Gekkouin focuses on firing his powers themselves with nothing sadistic spoken. He is willing to fight on other's behalf and acts pragmatically to stall for time then advise others to retreat as the next practical course of action when he himself is defeated.


During the time when Sika Madu was not the demon Shikama Dōji, Gekkouin was stood in between Asuramaru and Kiseki-o with Raimeiki and Byakkomaru surrounding Sika Madu as well. Selected as the first's chosen disciples Gekkouin was asked to help him save the world from the catastrophe that loomed in the far future. There was the option to decline since there would be no glory or reward available yet the answer 'yes' was given on whether they wanted to see this through.[2]

At some point, Gekkouin along with Sika Madu's rest apostles with Noya present as well are stood in a room surrounding him, as they watch him holding a young Yu who is unconscious as he stands near the clear casket containing the body of Michaela. In the room floating above them multiple black suns.[3]

Gekkouin along with the other demons who are Kiseki-o, Raimeiki and Byakomaru who are around Sika Madu enter the room where Noya, Ashera and Yu are. He remains silent in his position.[4]

At some point, Gekkouin was then sealed and cursed within a bow, and became part of the Black Demon Series.


Events of 2020

Second Shibuya High Arc

When Yoichi attempts to make a contract with a demon, Gekkouin takes over and forces Yoichi to relive his sister's death at the hands of the vampire Lacus. Gekkouin assumes the form of Tomoe and opens her deceased eyes as he has Yoichi relive his most traumatic memory in detail. He has the visualisation of Tomoe pull Yoichi out form under the bed and Gekkouin says because of him she is dead now.

As Tomoe he sits bored flicking a lamp switch on and off, then responds that Yoichi is the one who called him here and if he wants to avenge his sister's death he is going to need a strong set of cursed gear to wield. Regarding the form of Tomoe that he is taken and told it is pretty mean to look like that, Gekkouin replies to wait until Yoichi sees his true form. Turning to the matter at hand, Gekkouin feels there is a bit of a problem, Yoichi's desire is too weak and his soul is gentle and kind. Telling that Yoichi is lying about wanting to avenge his sister, Gekkouin says the strongest feeling he has is relief that he survived the attack. Further issues are that Yoichi would make a terrible fighter, is afraid of conflict and the thoughts of his friends and family getting hurt. Labelling him weak, without the courage to take a life, Gekkouin questions how Yoichi is to get revenge if he is not capable of killing. What Gekkouin really means is that Yoichi is a coward, just a child without a backbone. A black mist appears as Gekkouin explains one way to bring hell upon those who murdered his sister, by Yoichi giving him his body, forever. Tomoe's hand is used to stab into Yoichi and Gekkouin mocks the idea of Yoichi being a suitable master when he is the most pathetic human being he has ever met.

Posessing Yoichi

Gekkouin is successful in possessing him and the Yoichi demon hybrid's first act is the gain some distance from the magic circle it was in. Within a ceremony room perched on top of a demon statue, the creature counts four little humans all for it. Damning it since they each have cursed gears too, it remarks how power hungry humans are such a pain then calls for its bow. They will be its appetisers, then the real feast will begin. Firing and leaping across the room, the demon uses the physical bow to fend off Kimizuki's attack before kicking him. With the bow knocked out its hand by Yu, it then grabs Yu to throw him to the ground. Placing its hands up with Kimizuki's sword near it neck, the demon speaks to them that it is interesting they will not touch him because of the body it is in. Continuing to try and attack, the demon has regained its bow and tells Yu it is too late and to die. Faltering when Yu says he will not abandon a comrade, the demon begins laughing to itself. Appearing pleased when Yu casts his weapon aside, the demon calls him a fool as it takes aim. Yoichi breaks free of the illusion and says he wants the power to keep his friends safe, thus recovering the control over his body.[5]

Post-Shinjuku Arc

After becoming Yoichi's gear, Gekkouin is summoned by him and eliminates three horsemen at once. Yoichi has a high aptitude for controlling cursed gear, that he did this on his own without any training or coaching. This is normally impossible.

Yoichi reveals that he and Gekkouin chat in his dreams, and even discuss about their favorite colors.

Flying at Crowley

Nagoya Arc

At Nagoya City Hall, Shinya and Yoichi prepare to snipe at Thirteenth Progenitor Crowley Eusford. Yoichi fires Gekkouin at him but Crowley catches the manifested Gekkouin with his hands. Unharmed, he then flings it aside.

Osaka Arc

Gekkouin reappears in chapter 51 in Yoichi's mind. Gekkouin reminds Yoichi of his sister’s death and asks him why he is not getting angry. Yoichi tells him to stop and to make the illusion go away. Gekkouin refuses, stating that Yoichi will forget about his revenge if he does that. Yoichi says he is not running away and points out that even Gekkouin cannot handle all of the high-ranking vampires.

When Gekkouin says he will get help from Yoichi’s buddies, Yoichi says he refuses to get them mixed up in his revenge. Gekkouin says Yu is using Yoichi for his problems and is taking advantage of them to get his family back, but Yoichi says that is completely different. He explains that Yu is a nice person who refuses to give up and keeps trying to get his family back and to protect his friends. He says that is truly amazing and insists that despair and hopelessness would have devoured him if he had not been lucky enough to become part of his family.

Gekkouin points out that Yoichi is implying he is not nice like Yu, and Yoichi agrees. He says he is so mean and nasty and petty that he cannot let the others find out. He explains to Gekkouin that they must make Lacus suffer and cannot kill him quickly or cleanly, but they cannot let his friends know. Gekkouin laughs and agrees to help him.

Post-Shibuya Arc

Using one of Kiseki-o's coffins Gekkouin enters his realm to join him and Asuramaru there. Stating that he took long enough to call for him Gekkouin confirms with Asuramaru that his memories have returned which occurred the moment the king woke up. Wondering why Kiseki-o has a large hole in his chest Gekkouin questions whether he is going to be okay. He then asks what about Raimeiki and Byakkomaru. Their plan involves opening a path to pour desire into the king's world to sustain it and Gekkouin remarks that would be bad if the king escaped before they could do that since master Sika Madu would be disappointed in them.[6]

Noticing a large spiked cross jabbed through one of Kiseki-o's coffins nearby Gekkouin questions if that is one of the king's attacks. Saying that he feels strong Gekkouin adds they should have expected as much from the first's child. Feeling that he is going to need a little more power than usual Gekkouin breathes before calling to Yoichi. He promptly receives it as an aura envelops his hand and multiple arrows appear above him. On how easily it was to acquire power Gekkouin answers Asuramaru that he got lucky and found a decent guy before asking if Asuramaru is not that close with his human. With Kiseki-o ready Gekkouin is prepared to enter one of the coffins that stays open when they are being struck by the king. He directs his arrows which fly through the portal opening of a coffin.[7] Gekkouin along with Kiseki-o and Asuramaru have gained access the world where the young Mika is with something that looks like Yu. Stood on a rooftop they observe Mikaela stood in the centre of them.[8]

Whilst he stays out of the fight that Asuramaru leads[9] Gekkouin is ready to enter through Kiseki-o's coffin to successfully strike Mikaela's arm with an attack while he was distracted. Stating that Mikaela may be the first's kid Gekkouin points out that when it is a three on one, they win especially when it is them three.[10] He stands behind Mikaela who is tearful having failed to stop Mika from stabbing his family due to Asuramaru's influence. As Kiski-o says for them to get Mikaela bound Gekkouin asks about the first. He replies it is good at hearing that he will wake soon then joins Asuramaru and Kiski-o in placing their hands over the subdued Mikaela.[11] Seeing that Asuramaru has had his arm suddenly dismembered Gekkouin further processes the scene of Yu breaking out of Asuramaru's chest.[12] On Asuramaru's direction Gekkouin carries out the act of not letting Yu touch the king by taking Mikaela away with Kiseki-o.[13]

Feeling that Ashera's presence has vanished, with Kiseki-o it is discussed whether he was taken out. Sensing intense power Gekkouin questions whether Kiseki-o thinks they have a chance of taking it. Deeming it kind of amazing Gekkouin wonders how many centuries it has been since something this unexpected happened. He also asks whether Kiseki-o thinks this is all still part of Sika Madu's plan but they have just been excised from it. After recalling being with Sika Madu in the past Gekkouin decides if this is something Sika Mdu did not foresee then this is where they show their stuff, they cannot afford to fail. Leaving the king to Kiseki-o he asks how long it would take him to crush his heart and take Mikaela in. When Kiseki-o replies he does not have the skill Ashera has Gekkouin encourages him to find that skill and fast. With ten minutes needed Gekkouin states he will buy Kiseki-o that time.[14]

Seeing a bolt of lightning in the sky Gekkouin reaffirms his commitment to the ten minutes and vows to use every scrap of his strength. Alerted to Yu behind him Gekkouin has his left arm cut off before responding with his Thousand Arrows of Light power. The flurry of projectiles is avoided and seeing Kiseki-o assist him Gekkouin states he told him to focus on the king. A shimmering line is drawn and Gekkouin has the One Thread, One Glint go towards Yu's face. The string is avoided but smashes apart the landscape and buildings it sweeps across yet Gekkouin shouts how did that not hit Yu after he avoids it.[15] While another One Thread, One Glint is prepared, with Yu overcoming Kiseki-o's attack Gekkouin hesitates then speaks for a Thousand Arrows of Light. Informed that he is too slow Gekkouin is then sliced apart at the waist and head. Before he falls Gekkouin presses Kiseki-o to run and warn Raimeiki and Byakomaru.[16]

Sat facing Yoichi in his mind Gekkouin's hair is taken as he is made to look at him. As Yoichi expresses his resolve on the importance of family to him Gekkouin attempts to have him listen since they have reasons. Weakened with it difficult to communicate Gekkouin tries to reveal their cause. Told he is done Gekouin damns the situation and begins fizzling away. In the world that Mika is in he lies on his back motionless.[17]

The Gekkouin bow is generated when Yoichi summons it upon Guren's order for everyone to restrain Yu when there is the matter of restoring the world at stake.[18]

Powers and Abilities

  • Demon's thrall: Gekkouin can enter his host's memories and dreams to create nightmares of his host's past in order to break his host's will and take over their body. This ability may only be used against the demon's host.
  • Power enhancement: With his close connection with Yoichi he can call upon him for power. Practically an aura envelops his hand and the arrows Gekkouin means to direct at enemies appear.
  • Basic form: Gekkouin takes the form of a big black bow with glowing eye-like parts at the upper and lower curves of the bow . It is a purely long-range Cursed Gear.
  • Miniature form: A compact form of the weapon. It is easier to carry and to hide. A special ability of manifestation-type weapons.
  • Arrow manifestation and sniping capabilities: Gekkouin can manifest multiple arrows and can see far away. This allows Yoichi to target multiple enemies as well as spot them before they can attack. He can guide these arrows using his hand to fly into a portal at which point they can hone in on an unseen foe. A projectile fired at close range that managed to hit Mikaela was powerful enough to blast his arm off.
  • Thousand Arrows of Light: With one hand held outwards Gekkouin could fire a burst of projectiles all at once.
  • One Thread, One Glint: A taut shining string appears almost horizontally before Gekkouin. Instructed to go it is no longer glimmering as it curves outwards towards its target. The thread becomes humongous as it ploughs across everything before it. The shimmering light is explosive like a violent wave of fire and the strand can slice cleanly through buildings with the force to lift sections into the air.


Yoichi Saotome

Gekkouin's contractor Yoichi Saotome, who was able to learn his name and access his most traumatic memories. Appearing bored at Yoichi on account of his kind nature, as Tomoe he takes ahold of his face and calmly explains the problem. Although Gekkouin initially wins possession of his body, Yoichi's feelings for his friends soon give him the willpower to regain control. That as well as wishing to do something to help them when he could not before for his sister. They later become friendly and chat in Yoichi's dreams, even going so far as to discuss their favorite colors. He has tremendous balance and potential. Gekkouin can call upon Yoichi for power and have it granted. Hearing he is on good terms with his human Gekkouin answers that he got lucky and found a decent guy. Confronted by Yoichi he tries to explain there is a reason behind the fight involving Yu and Mikaela.


Where Gekkouin is bound to Yoichi's cursed gear bow, Kiseki-o was bound to the twin swords that were kept in the same black demon area that Yoichi's team member Kimizuki acquired. He is familiar with this other black demon and casually greets him after accepting the coffin entry point into his realm. Gekkouin expresses concern for the injury Kiseki-o has sustained. With them working together to stop Mikaela from escaping he encourages Kiseki-o to heal up. Gekkouin fires his arrows through one of Kiseki-o's coffins in an attempt to gain access to the world where Mikaela is.

I'll leave the king to you. How long will it take for you to crush his heart and take him in?

–Working with Kiseki-o and intending to buy him time to crush Mikaela's heart "He's Calling for Me", page 18

Advising that Kiseki-o be the one to crush Mikaela's heart Gekkouin fights on his behalf to buy time. Overpowered Gekkouin tells Kiseki-o to escape and warn other demons.


A fellow black demon, Asuramaru is bound to Yu's cursed gear. Sharing how his memories returned he then asks Asuramaru about one of the king's attacks. Discussing the humans they can call for power from Gekkouin asks whether Asuramaru is that close to his. They work together to remove Mikaela's desires and have him captured for the first.


Kureto's demon Raimeiki, who Gekkouin thinks to get involved in a five way plan involving containing Mikaela. They were present before Sika Madu together in the past.


Shinya's demon, Byakkomaru, who like Raimeiki is excluded from Gekkouin, Kiseki-o and Asruamaru's plan as backup in case they should perish. They were both selected as Sika Madu's disciples.

Demon Mika

The Mika who has returned as a demon. Gekkouin's memories returned as soon as the king as he refers to him to awoke. He feels it would be bad if the king escapes since Sika Madu would be disappointed in them. Commenting that he is strong Gekkouin expected as much from the first's child. Able to land an attack on him Gekkouin speaks that it was a three one one fight that allowed them to win over the first's kid. Taking Mikaela away from Yu, Gekkouin means to help Kiseki-o crush his heart.

Sika Madu

The first progenitor who went by the name Sika Madu during the dark ages of Greece. Gekkouin was selected as one of Sika Madu's disciples to help him save the world in the far future. When the first is now Shikama Doji, Gekkouin refers to him as "Master Sika Madu" and means to help contain his son Mikaela so that the first will not be disappointed in him, Asuramaru and Kiskei-o. Even though it is possible that he has been excluded from Sika Madu's plans Gekkouin remains loyal. Either way he intends to fight against a foe who possibly defeated Ashera to buy time to progress with what he feels the first would want.

Yūichirō Hyakuya

Whether he was aware of Asuramaru's human or not, Gekkouin reacts to Yūichirō Hyakuya's presence by keeping Demon Mika out of his grasp. Resolving to fight Yu to buy Kiseki-o time and after having his arm sliced Gekkouin deploys two powers, the Thousand Arrows of Light, and the One Thread, One Glint powers to attack Yu with. Gekkouin is largely soundly defeated by Yu as a demon who had three seraphs at his back.


Image gallery: Gekkouin


Hmm... Dangerous humans. I'd better kill them all.

–Gekkouin after possessing Yoichi. "Black Asura"

Well? What now? Do you want power? I rifled through your heart, but I couldn't find any truly strong desire for revenge. All I found was stability. Kindness. Concern for others. I can't stand any of that. My sustenance is greed and desire.

–Gekkouin to Yoichi Saotome ."New Family"

Lies. You were saved... and that makes you glad. You don't like fighting. You hate the thought of friends or family dying. And you can't stand the thought of killing anything yourself. You want revenge, but you can't kill? C'mon. You don't have nearly enough greed. Wishy-washy humans like you... I hate. So I think I will become you and get revenge for your sister in your place. Give me your body, Human. You don't even have a strong enough desire to resist. No, you will not do at all. You are not fit to be my master.

–Gekkouin to Yoichi Saotome. "New Family"

Your sister was killed. Remember? Killed in cold blood by that Lacus vampire. He's standing right there, and you still aren't getting mad? Wuss.

–Gekkouin to Yoichi Saotome. "Crucifying the Immortal"

Really. Then, let me take over your body. I'll kill that blood-sucker for you. I'll kill him good.

–Gekkouin to Yoichi Saotome. "Crucifying the Immortal"

Yeah, but that Yu guy is totally using you for his problems, y'know. He seems a-ok with taking advantage of you guys to get his family back. Turn-about is fair play.

–Gekkouin to Yoichi Saotome. "Crucifying the Immortal"

Uh-huh. So you're implying you aren't nice like him?

–Gekkouin to Yoichi Saotome. "Crucifying the Immortal"

You got it. See? This is why I like you, Yoichi.

–Gekkouin to Yoichi Saotome after he reveals his intention to torture Lacus. "Crucifying the Immortal"

Hey, um, why do you have that big frickin' hole in your chest? You gonna be okay?

–Recognizing an injury and expressing concern for another demon, Kiseki-o "The King's Chambers" page 14

Yeah, that'd be bad. If the king escapes, master Sika Madu will be disappointed in us.

–Feeling it would be bad if Mikaela escaped. Addressing Shikama Doji by his past name of Sika Madu who Gekkouin addresses as master. "The King's Chambers" page 15

He feels strong. Should've expected as much from the first's child.

–Able to sense Mikaela's strength when they are not in the same area together. Aware that the demon is Sika Madu's son (and the first confirmation in the manga that this was the case). "The King's Chambers" page 16

Aah! You may be the first's kid, but when it's three-on-one, we win! I mean it's us three!

–Having blasted Mikaela and with Asuramaru having reached Yu and Mika he speaks of why along with Kiseki-o they won. Chapter 100: "A Demon Appears," page 37

This is kinda amazing. How many centuries has it been since something this unexpected happened? Or do you think this is all still part of master Sika Madu's plan? And we've just been excised from it?

–The view on Yu appearing to interfere with the plan for Mikaela, and considered he and Kiseki-o have been left out of Sika Madu's plan. Chapter 102: "He's Calling for Me", page 16


  • In the rough draft for chapter 51, Gekkouin's real form was originally supposed to have long hair rather than short hair.
  • Where Sika Madu had said that the Mikaela from ancient Greece was his son, in chapter 98, Gekkouin stated that Demon Mika was the first's child supposedly linking the two as the same.