|Manga debut||Chapter 35|
|Anime debut||OVA: Red Knife Wielder|
Domon was a police officer in Tokyo. He was Senji Kiyomasa's superior, mentor and friend.
Domon had short, messy hair that is grey at the top, but black at the sides. He had a goatee. He is always seen with his police uniform, a white shirt with a black tie and black trousers. He also wore his police belt with a gun, handcuffs and various other things.
Domon was very clear-headed. He knew much about the world and could see right through people. This is how he also obtained much knowledge of human nature, that he then shared with Senji. He cared much for his fellow policemen and tried to raise them. He was also very protective of Senji. Also, he had a right sense for justice, thinking that policemen who beat up punks, are just as bad as them. According to Senji, Domon was very righteous. Domon is also an avid smoker.
Some time after the Great Tokyo Earthquake, he and his team (including Senji) were assigned to Tokyo, in order to keep the rampaging under control. In that time, Senji already had his Branch of Sin and used it to defeat the thugs. He and the other colleagues relied much on Senji, who he often offered to smoke a cigarette, but Senji kept declining, saying that you die because of cigarettes.
One day, Senji got a message from Ikazuchi Akatsuki, challenging him to a last battle. Senji was going to go, teaching the youngsters a lesson. He told Domon to just rely on him. As a reply, Domon punched him in the stomach. He gathered his team and they went to the challenge instead of Senji, protecting him.
When Senji was finally able to follow them, he heard Domon's voice calling him. He went to where the sound was coming from and saw Domon and the others brutally slaughtered by Akatsuki and his men. Domon asked Senji to pass him a cigarette, to which he was reaching with his severed arm. Senji collapsed on his knees next to Domon and cried , saying that he should be the one relying on him. Domon says that Senji was such a burden to him and called him a brat. He said that depending on others is a specialty of kids. He told Senji that he too would actually feel good when being relied on,and that that day will come for him too. He ends with saying that if depending on others is a specialty of kids, than acting all cool is a specialty of adults. He died very shortly after that.