Age: 16
Bloodtype: O
Birthday: May 5 (Taurus)
Madougu: Dosei no Wa ("The Ring of Saturn"), Kuchibashi Oh ("Beak King"), Tetsugan ("Iron Ball")

Domon is Recca's schoolmate who is known for his prowess in physical strength and in fighting (he is referred to as Ogre (鬼 Oni) by other students that he has defeated in fights). Like Fūko, has always wanted to defeat Recca, and the reason behind this is that Fūko told him that he could only challenge her if he manages to defeat Recca. He is unable to defeat Recca despite his numerous attempts, and he eventually aids the latter in defeating and rescuing Fūko when she is brainwashed by Kage Hōshi. Afterward, both he and Fūko join forces with Recca and remain allied with him throughout the rest of the series. However, he is never able to do so, and ends up befriending and joining forces with Recca. Domon wields the Dosei no Wa ("The Ring of Saturn"), a madogu which enhances his physical strength. Later in the series, he also wields the Kuchibashi Oh ("Beak King"), a super-sharp snapping claw on an extendable chain, and the Tetsugan ("Iron Ball"), which transmutes his entire body into a living iron golem for brief periods.

Domon is depicted as someone who is physically strong with matching endurance (even before acquiring his Madogu), but intellectually inept. Another of his assets is his strong will-power, which is recognized even by one of the series' antagonists, Kurei, after Domon manages to thwart Noroi's efforts to erase his memories due to his will-power. Domon is also at times something of a pervert, though his attribute actually proved useful against his fight with Kirin. It is openly shown that Domon is interested in Fūko romantically, although he is prone to getting attracted to other women as well.