I don’t think he was vomiting cuz of the kiss but perhaps of another reason which might be uncovered in the next season. It might be his body rejecting itself or something(I’m delusional)
I read a reallyyyy good comment here that had the theory that maybe he vomited because he was reluctant to kiss Jinwoo. It seems like he craves someone who will stand up to him, and Jinwoo kissing him would mean he is attracted to him and therefore, just like the others in the group that just do what Guwon wants.
That would be why he says he is too attractive for his own good. However, after having a good night's sleep with him, he realizes Jinwoo is what he needs, and after Jinwoo stands up to him, boy is obsessed.
I liked that theory, because it fits the circumstances, but of course, we don't know yet!
What I dont get is
When guwon vomit(? I think he was vomiting) after the first kiss scene. I thought he dont like it and just play along with jinwoo... Also he talk to the mirror like the body is not belong to him. Im itching to know whats in guwon POV this is so good