He wasn't in it.
This biseinen is first introduced in the 7th manga, Rhapsody, and has a very tragic past. He was deeply in love with a girl he only ever met through dreams, Hokuto. But she died, and when he found out he was assuaged by grief and tried to commit suicide, unsuccessfully. Now he's kept alive only through the life support machine in his private hotel room.
I'm unsure why he is a member of the Chi no Ryu... He is also a dreamseer, like Hinoto, Kanoe and Kotori. When she is drive insane by Fuma, he protects her, and when Fuma finally kills her, Kakyou takes the pain for her. As she travels off, she tells him to tell Kamui she loves him (or something like that). I read somewhere that maybe he is a member of the Chi no Ryu because he knows of Fuma's impending insanity and hopes he will kill him. It's an interesting idea, but I'm unsure. Maybe, through the death of his destined soulmate, he lost all faith in humanity and would rather see the Earth recover from them - then surely his own death would be sealed along with the rest of mankind and he can rejoin Hokuto. Perhaps, through his dreams, he saw Fuma destroying the Chi no Ryu and thought that by joining them, Fuma could bring him to his end more quickly. I guess I'll only know when Viz release more of the series here and I can find out.
X Japan song:
Rose of Pain. I don't know why, but it seems to suit him a little... Also, ironically, 'Alive' makes me think of him also.