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Yūichirō Hyakuya

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Yūichirō Hyakuya
Yūichirō Hyakuya
Name Yūichirō Hyakuya
Kanji 百夜 優一郎
Vital Statistics
Race Human/Seraph of the End Hybrid
Gender Male
Age 16
Birthday 2004
Professional Status
Affiliation Japanese Imperial Demon Army
Section Moon Demon Squad
Rank Special Second Class Soldier;

Buck Private (Formerly)

Demon Weapon
Series Black Demon Series
Demon Ashuramaru
Personal Status
Status Alive
First Appearance
Manga Chapter 1
Voiced By Miyu Irino
Image Gallery

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.


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. He is usually 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 underneath 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 is brave, fearless and somewhat reckless, as evidenced when he defeated one of the four Horsemen of the Apocalypse while ignoring orders which is noted not to be the first time. He is a very narrow minded person, whose goal is to annihilate all of the vampires because of what they did to his "family"; overcoming any type of challenge in order to accomplish it.

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' like Felid Bathory. Also he empathises with others who put their family first, as seen when a civilian girl gave them false information because she was threatened by a vampire that they would kill her parents. After finding out about this, he told the girl that she did the right thing to save her family. After recovering from his coma, Yūichirō has grown more mature, as quoted from Shinoa. And after he overcame his worst nightmare, he became more defiant, still having the naivety trait when trying to befriend his demon weapon, Ashuramaru.

It is later revealed that his goal, rather than revenge, is to protect his new friends and family, in order to avoid a repeat of past events.


In 2012, Yūichirō's father tried to kill him and his mother kept raving about how he was a demon spawn. Then she lost her mind and killed herself which lead to him being sent to the Hyakuya Orphanage on Christmas day. There he was introduced to  Mikaela and the other orphans. Seeing as the two 8 year olds were the eldest,  Mikaela wanted them to be friends. However, Yūichirō was very distant towards him. Mikaela made it very clear he was the leader, so he punched Yūichirō. Afterwards, he told Yūichirō that he used to be alone like him, but now he had a big family. And from that then on, he had one too. Yūichirō proceded to tell Mikaela of the circumstances that lead to his being there. Then Mika told him with a smile that he was abused by his parents, and then he was dropped out of a car and taken in by the orphanage. The other children then told him their stories. Mikaela then told Yūichirō that they weren't lonely because that day was the day their brother Yuu joined them. During the meeting the director suddenly began to bleed from her nose and mouth, and fell to the ground.

Then while outside they saw as the city was engulfed in flames. They had been attacked by the vampires lead by Kururu Tepes. For the next four years, they lived their lives as livestock for the vampires.

After Mikaela gained possession of a map of the underground, both of them decided to escape the place with the rest of the chidren from the orphanage.However it is revealed that Felid Bathory, one the Seven Founders, knew of this and killed the other children except for him. After reaching the outside world, he is found by Glen Ichinose, a captain of the Japanese Imperial Demon Army. In order to take revenge for his family, he decides to join the Japanese Imperial Demon Army to gain the power he needs.

Sometime after escaping, he was experimented on and was created into a being that is not human by Glen and the Army.


Four years later, Yūichirō became a private of the Japanese Imperial Demon Army. He still attended school as it was essential in life. And when he was told  'to make a friend', Yūichirō struggled as he considered that he didn't need any and that he hasn't made friends before.

Powers and EquipmentEdit

Natural AbilitiesEdit

Yūichirō seems to be a excellent swordsman, as he was trained by Glen himself, seen when he killed a Horseman of the Apocalypse using only a sword.

Demon WeaponEdit

  • Ashuramaru
  • Ashuramaru 「阿修羅丸」: Ashuramaru 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 Ashuramaru to fully use its power to attack opponents. His type is possesion.


  • It has been confirmed that he has part of him that is inhuman.
  • Since he lived in a vampire city for 4 years, he was able to learn to read and write in English.


  • 'If Mich needs me... If Glen, Shinoa, Yōichi and Kimizuki need me, then I don't care if I'm a devil or anything.' - Yūichirō to Ashuramaru in The Demon's Nightmare.



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