Yūichirō Hyakuya

Yūichirō Hyakuya 「百夜 優一郎, Hyakuya Yūichirō」 is a member of Japanese Imperial Demon Army's Moon Demon Squad and is the main protagonist of the Owari no Seraph series.

Appearance
Yūichirō has medium length black hair which can be considered quite messy. He possesses sharp green eyes which fall under his thick eyebrows, His eyes are large compared to most other male characters in the series. At the beginning of the series, he is often shown wearing a typical Japanese school uniform with a white sleeved T-shirt beneath.

After joining the Imperial Demon Army, he takes on their uniform consisting of a black jacket with light green details, and dark gray trousers and black boots which go over his trouser leggings. Yūichirō keeps his sheath on the left side of his hip. Sometimes he can be seen wearing the Japanese Imperial Demon Army hat. He often wears the JIDA cape as well.

Personality
He is brave, fearless and somewhat reckless, which is shown in the beginning of chapter 2 when he attacks a Four Horsemen of John while ignoring orders. It is noted not to be the first time. Yu is often called an idiot by those who know him. He is a very narrow-minded person, whose goal is to annihilate all of the vampires because of what they did to his "family," and he will overcome any type of challenge in order to accomplish it. He swears to kill all vampires because they killed Mika.

Despite this, he has a soft spot and worries about his friends first and his goals second. Some (mostly vampires) consider his personality as 'cute,' such as Ferid Bathory. Also he empathizes with others who put their family first, as seen when a civilian girl gave them false information because vampires are holding her family hostage. After learning why she deceived them, he tells the girl that she did the right thing to save her family. He is obsessed with Mika, having nightmares about Mika's death repeatedly for the four years until he makes friends with Shinoa and Yoichi. After learning Mika is alive, Yūichirō's personality changes in response and he grows more mature, as noted by Shinoa. He puts more effort into being patient and calm and making friends. His dream of genocide takes second place to reclaiming Mika. Even though his best friend is now a vampire, Yu still slaughters them without mercy or hesitation. He becomes closer to his squad members and Guren as well, making them promise to help him take Mika back. Friendship and bonds become more important to him. While in a mental battle against Asuramaru to gain more power or else lose his body to Asuramaru, he even calls Asuramaru his friend and convinces Asuramaru to yield to him.

Rather than revenge, his primary goal changes to protecting his new "family," in order to avoid a repeat of past events. In Nagoya, he surprises Narumi's squad by memorizing all of their names and promising to protect them.

Similarly to how vampires do not bother to remember human faces and only think of them as "humans" or "livestock," Yu only sees vampires as "vampires" or "bloodsuckers" without bothering to remember their names or faces. He does not even recall the name of his vampire target in Nagoya. The exception to this rule is Mikaela Hyakuya. He also appears to recognize Ferid Bathory.

History
Yūichirō Amane was born in 2004.

During his childhood, both of his parents screamed that he was demon spawn. Yūichirō's father and possibly mother tried to kill him. His father screamed that he had to kill the seraph of the end now or else the world would be ruined. His mother went mad and committed suicide, and Yu's home went up in flames.

This lead to Yu being taken to the Hyakuya Orphanage in Tokyo while being told he could meet friends who were just as unwanted as he was. This was on Christmas in 2012. He met Mikaela and the other orphans. Seeing as the two 8-year-olds were the eldest,  Mikaela wanted them to be friends, but Yu rejected him. Mika asked if Yu were challenging him to a fight and said he was the leader. They fought, and Mika gave him a serious smack-down. Afterwards, he told Yūichirō that he used to be alone like him, but now he had a big family. And from that day onward, Yu had one too. Yūichirō told him about his parents' violent behavior, saying that "family" no longer meant anything to him. Mika smiled, saying that both of his parents abused him until they got sick of him and threw him out of a moving car. The orphanage took him in after that. The other children shouted out their stories, saying that they never met their parents, their parents committed suicide, or their parents left them at the orphanage door. Mikaela then told Yūichirō that they weren't lonely because that day was the day their new big brother Yu joined them. Shortly after, the director suddenly began to bleed from her nose and mouth and collapsed to the ground.

The adults perished, and Third Progenitor Krul Tepes lead the vampire invasion on Tokyo. For the next four years, the orphans survived as livestock for the vampires in the vampire capital of Sanguinem, which is located under Kyoto.

Yu and Mika encounter Ferid, who asks them for a threesome, but Mika agrees to go while declining politely for Yu, claiming Yu to be "shy." After Mikaela steals a gun and a map of the underground, they made a daring escape attempt with their orphanage family. Unfortunately, this was all a trap set by a seventh progenitor named Ferid Bathory, who had relations with Mika. Ferid slaughtered the other children in front of Yu and Mika. Yu managed to shoot Ferid in the head, but Mika was fatally wounded. Yu called Mika "family" for the first time. He refused to leave Mika behind until Mika yelled at him and pushed him away. Yu escaped, leaving Mika behind; this action haunted him for years afterward. After reaching the outside world and realizing the vampires lied about the world's destruction, Guren Ichinose of the Japanese Imperial Demon Army finds him.

Guren mentioned a prophecy and knew that Yu was one of the lab rats from the Hyakuya laboratories. He was one of the children that was being experimented on by the Hyakuya Church to create a weapon of mass destruction, as part of the 'Seraph of the End' plan in destroying the world. Guren knew of this beforehand, thanks to intel provided by Mahiru in 2011. In order to take revenge for his family, Yu joined the Japanese Imperial Demon Army as Yuichiro Hyakuya.

Story
Guren agrees to give Yu the power to kill vampires when they first meet, but he does not put Yu in a vampire extermination unit right away. Four years later, Yūichirō is a private of the Japanese Imperial Demon Army. He gets suspended from the army for disobeying orders and is forced to attend Shibuya High School #2 in the meantime. When Shinoa tells him his suspension will continue until he makes friends, Yūichirō struggles since he has stubbornly rejected forming close relationships since Ferid Bathory slaughtered his family. He insists he does not need any friends. Shinoa gives him a note from Guren specifically written with the orders to make a friend; he promptly wads it up and throws it to the floor. With a little persuasion from Shinoa, he steps in to save Yoichi Saotome from bullies. Unfortunately, Shinoa tells him his punishment will be extended if he harms any civilians. Yoichi tells him he wants to join the army to get revenge for his sister's death, but Yu tells him to forget the army and that his sister wouldn't want him to avenge her death. An emergency warning goes off, and Yu challenges the escaped vampire assailant, nearly killing her when Guren arrives and ends her life. Yoichi becomes Yu's friend, meaning that Yu actually reached the requirement Guren gave him. In a dream, Yu's orphanage family tells him farewell.

In chapter 3, Yu learns that Shinoa has a demon weapon for slaying vampires and wants to take it from her by force. She rapidly relieves him of that notion. Yu, Shinoa, and Yoichi save Yamanaka's friend Yuji. During the fight, Yu makes contact with the myo-o demon but breaks out of the demon's illusion on his own, surprising Shinoa. She agrees to notify Guren.

In chapter 4, Yu meets and fights with Shiho Kimizuki before attending his first class in the Moon Demon Company Barracks. Guren introduces Yu as the idiot and Yoichi as the crybaby. Yu gets paired with Kimizuki for a practice test. When Kimizuki's sister goes into critical condition, Yu punches Kimizuki and convinces him to go see her during the middle of the exam. They become friends and rivals. Shinoa recommends both of them for the Black Demon Series.

Although Yu earns a zero on his spellcraft exam, which is supposed to help determine what rank of cursed gear he can receive, Yu is permitted to try for a Black Demon Series weapon along with Yoichi and Kimizuki. He appears to be nearly illiterate since he used no Kanji on his exam and wrote everything phonetically. Yu challenges Asuramaru, earning the demon's power in order to protect everyone, and Asuramaru informs Yu that 1/10th of him is not human. Afterward, Yu talks to a possessed Yoichi and helps him to regain control over his demon Gekkouin.

In chapter 8, he meets Mitsuba Sangu, who completes their 5-person squad. A Four Horsemen of John chases a young girl. Against Shinoa and Mitsuba's orders, Yu rescues the girl, and a group of vampires attack him. Mitsuba slaps him for his disobedience, but he declares he does not regret his decision. In the following chapter, they use information from the girl to lead an attack against the vampires. Although the vampires seize Mitsuba, Yu's strength shines through, and he rescues her. Even though the girl deceived them, informing the squad that there were only seven vampires instead of nine vampires, Yu tells her she did the right thing to protect her family.

Before they head to Shinjuku, Kimizuki hotwires a hummer. This impresses Yu, who says he had not been in a car since he was little and anyone rarely uses cars in Shibuya since gas is such a precious commodity. Yu attempts to drive and nearly accidentally crashes into his squad members, leading Kimizuki to violently remove him from the vehicle. Kimizuki promises to teach him how to drive on another date. As they head to Shinjuku, they encounter Thirteenth Progenitor Eusford Crowley. Yu manages to take his right arm momentarily before Crowley is summoned away by Seventh Progenitor Ferid Bathory.

They reach the battlefield in Shinjuku, and Guren summons Shinoa's squad to the 5th Street intersection. After taking his supplement, Yu charges into battle, saving Guren's life by stabbing Mika through the chest while Mika was too stunned to react.

Horrified, Yu freezes. Guren attempts to exterminate Mika, but Mika escapes. Guren hits him, but Yu says that person is Mika, his family. He cries from happiness. Ferid attacks, but Mika cuts off Ferid's arm when he touches Yu. Mika asks Yu to run away with him, but Yu does not want to leave his friends. Screaming, Yu's left eye becomes dark and appears to bleed while a massive wing-like structure sprouts from his left upper back. Muttering that he must kill all sinners, Yu approaches Shinoa. When Yu attempts to kill her, Mika protects her but is stabbed in her stead. Guren orders Shinoa to embrace Yu, and she hugs him, effectively ending his transformation and sending him into a coma.

Yu wakes up exhausted a week later.

He looks up books on vampires to try and learn how to turn Mika back into a human. Later, Lieutenant General Kureto Hiragi summons Yu to the Shinjuku Central Army Headquarters First Office where Kureto sicks a starving unarmed vampire on him. Yu kills the vampire without hesitation. Kureto challenges him to a duel but cheats, winning quickly. He then attacks Kureto while his back is turned, but his aide intercepts. Kureto tortures Yoichi and Kimizuki to try and get information from Yu. He tells Yu about the Hyakuya sect, asking if Yu was from that family. Yu knows nothing about the Hyakuya sect.

Guren tells Yu he knew about Yu's connection with the sect all this time, and he agrees to help Yu get Mika back. Shinoa and Mitsuba teach the squad about possession- and materialization-type demons. Yu weakens the curse binding his demon before Kimizuki and faces illusions of his orphanage family and his biological family. After Kimizuki conquers his demon as well, the two spar. Both of them use special abilities, which should be impossible for the possession-type demons they use. Yu uses a technique called "Asura-Kannon," ordering it to fan-out; this produces numerous materialized swords.

Shinoa tells Yu about what he really did on the battlefield of Shinjuku, and they agree to side with Guren in the upcoming political power struggle.

They depart for Nagoya, and Yu drives for the first time. When Guren scolds their squad for being tardy, Yu takes the blame. Yu meets Sergeant Makoto Narumi, tricking the sergeant into believing Yu is 20 years old until Guren announces otherwise in chapter 26. Guren, Mito Jujo, and Shinya face off against Shinoa's squad, handily giving them a one-sided beat-down before their commence their operation in Nagoya.

Shinoa and Narumi's squads team up with Shinya to exterminate Fifteenth Progenitor Lucal Wesker, and they do it successfully without any injuries to their squads.

The Moon Demon Company regroups, and Team Leader Aiko Aihara arrives with only seven survivors from her squads. Yu offers to keep watch while her squad takes a short rest. Guren Squad, Shinoa Squad, and Narumi Squad leave to hunt Thirteenth Progenitor Crowley Eusford, Seventeenth Progenitor Chess Belle, and Horn Skuld while Aiko waits for other survivors to pass them the order to reconvene at Nagoya Airport.

Natural Abilities
Yūichirō seems to be a excellent swordsman, as he was trained by Guren himself. This is shown when he killed a Horseman of John using only a sword. He is also a "seraph of the end" with 1/10th of him being not human; he may have been experimented on by the Hyakuya, but this is unclear since the adults in charge of him were killed minutes after he arrived at the orphanage.

Demon Weapon

 * Asuramaru 「阿修羅丸」: Asuramaru is a demon of the Black Demon Series. It resides inside a black sword that Yūichirō uses. Whilst in use, the blade develops a thick green aura. Like Shinoa Hīragi, he can call upon Asuramaru to fully use its power to attack opponents. This is a possession-type demon.
 * Asura-Kannon: A special technique using Asuramaru that materializes dozens of floating swords.

Experimentation

 * Drugging-up: Like other soldiers in the JIDA, Yu takes a supplement to increase his synchronicity with his demon to 150% for 15 minutes. After that time is up, this synchronicity drops to zero.  There are numerous unpleasant side-effects, and officers only resort to this as necessary.
 * Seraph of the end: By swallowing a special tablet produced by Guren, Yu can lose his mind and undergo a painful transformation. His left eye turns dark and bleeds while a massive wing-like structure sprouts from his upper left shoulder.  Although extremely powerful, he goes berserk and attempts to kill any human nearby.  The Progenitor Council is extremely concerned with his immense power in this form.  Guren causes this transformation to end by making Shinoa hug Yu.  Yu coughs up blood as the transformation ceases.  The drug takes five days to get out of Yu's system, and he spends the total of one week in a coma.  Even after that, he feels tired.  Yu has no recollection of the events that occur while he is transformed.

Trivia

 * 1/10th of him is not human.
 * Since he lived in a vampire city for 4 years, Yu is nearly illiterate and only writes phonetically without using any Kanji. Vampires have no need to educate livestock on how to read or write.
 * Yūichirō means "Superior First Son."
 * Hyakuya means "Hundred Nights."

Quotes

 * "GAH! I CAN'T TAKE THIS ANYMORE!!  It hurts!  It makes me dizzy!  And I can't stand those blood-suckers looking at me like I'm livestock!  What do they think we are?  Pigs?  Cows?  Chickens?!  That's why we've gotta start a revolution!  You and me, Mika.  We'll both get stronger, and then we'll go kill the vampire queen and turn this place into a human kingdom!"--12-year-old Yu to Mika in the streets of Sanguinem, Chapter 1, "The World of Blood Legacy"
 * "Who needs some stupid 'family'? I got sent here because my father tried to kill me.  My mom kept ranting and raving about how I was demon spawn.  She eventually went nuts and killed herself.  So do you get it now?  'Family' doesn't mean anything to me!"--8-year-old Yu to Mika the day Yu arrives to the orphanage, Chapter 1, "The World of Blood Legacy"
 * "Quit trying to shoulder all our burdens by yourself!"--12-year-old Yu to Mika in Sanguinem, Chapter 1 "The World of Blood Legacy"
 * "You're... my family. I... finally found a real family!  I can't leave you!"--12-year-old Yu to a fatally injured Mika, Chapter 1, "The World of Blood Legacy"
 * "You aren't Mika. Mika would never tell me to get revenge.  He was smart, but he was always stupidly nice to all of us.  SO WHO ARE YOU?!  HOW DARE YOU PRETEND TO BE MY FAMILY!!  I'LL KILL YOU!!"--Yu to a myo-o demon, Chapter 3, "The Demon in Your Heart"
 * "ARE YOU STUPID?! WHO CARES ABOUT POINTS?!  THIS IS YOUR FAMILY WE'RE TALKING ABOUT!  If they die, then... they're gone for good.  You won't ever see them again."--Yu to Shiho Kimizuki when told that Mirai Kimizuki is in critical condition, Chapter 4, "The Worst Pair"
 * "Once I have the power, I'll get revenge for the death of my family. Those bloodsuckers killed Mika, so I'm gonna kill them all!!  That's my one and only reason for living."--Yu before first challenging Asuramaru, Chapter 6, "Black Asura"
 * "DAMN IT!! SHUT UP, SHUT UP, SHUT UP!!  Just give me your power already!!  I... need it!!  I need enough power to protect everyone!!"--Yu confessing the truth of his feelings while confronting Asuramaru, Chapter 6, "Black Asura"
 * "I don't ever wanna say I survived because I left someone else to die ever again!!"--Yu to Shinoa's squad when he enters an obvious trap to save a human girl, Chapter 8, "Mitsuba's Squad"
 * "What was it you guys said? We humans are 'ugly'?  Trash that would sell out anybody if our family's been taken hostage?  Ha!  Sounds like you're real familiar with that little ploy.  You're right.  Humans will do anything for their families.  We'll happily lie, cheat, make deals with the devil, or even become demons ourselves.  If you wanna call that 'ugly,' then fear human ugliness when it kills you, Bloodsuckers!"--Yu to the enemy vampires in Omotesando Station, Chapter 9, "First Extermination"
 * "...'Those humans' are using me? What's that mean, Mika?  You...  You make it sound... like you aren't human anymore.  It's my fault, isn't it?  My fault for running away..."--Yu to Mika when they reunite, Chapter 13, "Reunion of Childhood Friends"
 * "S-s-ssi-sinners... S-sinners must... d-die.  M-must kill... all s-si-sinners."--Berserk Yu preparing to kill Shinoa, Chapter 13, "Reunion of Childhood Friends"
 * "Do not interfere, Vampire. All humans must be killed."--Berserk Yu to Mika when Mika protects Shinoa, Chapter 14, "Everyone's a Sinner"
 * "It wasn't a dream. And that means Mika really is alive.  Ha ha...  He's alive...  Ha ha ha...  I'm not dreaming...  He really didn't die...  Thank God...  I'm so glad!"--Yu to himself, after waking from a coma, Chapter 15, "Complicated Connections"
 * "Just you wait, Mika. I swear... I'll save you."--Yu to himself, Chapter 15, "Complicated Connections"
 * "...I was looking west. That's where Mika's gotta be, right?  In the vampire city.  I heard the place they held us was somewhere underneath Kyoto...  Someday, I swear... I'll go get him back."--Yu to Shinoa when asked what he was looking at, Chapter 18, "Possessed by Mahiru"
 * "I tried climbing back up using my sword, but some stupid janitor yelled at me for putting holes in the walls!"--Yu after returning from the roof Guren previously flung him from, Chapter 18, "Possessed by Mahiru"
 * "Whatever your reasons, if you hadn't rescued me that day, I would've died. I do still feel like I owe you for that.  So what I wanna know is...  Am I actually useful to you?  That's all.  I don't care what you and that Hiragi guy are fighting about.  I don't care what you're after.  All I want to know is, do you need me?  If you do...  Would you want Mika, too?  He was in the same orphanage as me.  If you do...  If you think you could need Mika like you need me...  Then, I'll be your guinea pig or anything you want.  I'll do everything I can to help you with whatever you need.  Just tell me how I can get Mika back!"--Yu to Guren, Chapter 18, "Possessed by Mahiru"
 * "Those words don't hurt me anymore. Besides, I don't care if I am demon spawn.  If Mika needs me..  If Guren, Shinoa, Mitsuba, Yoichi, and Kimizuki want me as their friend, then I don't care if I'm a demon."--Yu to Asuramaru, Chapter 20, "The Demon's Nightmare"
 * "I don't care if you're a demon. I need you, Asuramaru.  Join me, please.  We can be friends.  Help me rescue Mika...  He's family."--Yu to Asuramaru, Chapter 20, "The Demon's Nightmare"
 * "I... Um...  This is kinda embarrassing, but...  Well...  Guren said we're family now, right?  So you, Yoichi, Kimizuki, and Mitsuba...  We're all a new family.  And I've started to feel that's true.  You guys are important to me.  But...  I can't forget Mika.  He's also an important family member.  See...  My parents abandoned me.  So maybe I don't really know how families work.  But can I ask you guys this?  Just because someone in your family betrays you, does that mean you have to betray them back?  I don't... think it works that way.  So even if Guren betrays us... and Mika, well... even if he is a vampire now... he's still family. We're all still family, and we always will be."--Yu to Shinoa's squad, Chapter 23, "Ambition in the Demon Army"