Yūichirō Hyakuya 「百夜 優一郎, Hyakuya Yūichirō」is the main protagonist of the Owari no Seraph series. He is a member of the Japanese Imperial Demon Army and Shinoa Hīragi's squad in the Moon Demon Company. He, along with Mikaela Hyakuya, possesses the "Seraph" gene, which is relevant to the forbidden taboo and the focal point of the story, "Seraph of the End."
He is brave, fearless and somewhat reckless, which was shown when he attacked a Horseman while ignoring orders. It is noted that this wasn't the first time. Yū is often called an idiot by those who know him. He is a very narrow-minded person, whose only goal is to annihilate all vampires because of what they did to his "family," and he will overcome any type of challenge in order to accomplish it. (owarinoseraph.wikia.com)