Kio Kaidou

He is a friend and classmate of Soubi's. They are both art students, and in volume 6 Kio tells Ritsuka, "I'm probably Sou-chan's only friend." It is all but explicitly said that Kio is homosexual. Most of his early dialogue is filled with flirtations and passes at Soubi, despite being gently ignored or indirectly rejected each time.

Despite his early presence as a character who exists solely to create a lighter atmosphere among a very dark story, he gradually gains depth and justifies his existence as the story progresses. He becomes a loud voice that champions pacifism and self-worth. This contrasts strongly against Soubi's submissive nature that willingly accepts violent treatment and strongly desires to be completely controlled, albeit from only very certain people. More significantly, Kio's views are shared by Ritsuka. Together, they provide a very black-and-white atmosphere that allows only one line of thinking.

It was recently revealed that Soubi only became interested in Kio because of a tattoo on his back, and a vow that he took when he got it.