
That bugged me too, at first I thought he was throwing up out of disgust after kissing him, like he was faking it in order to mess with him. However, I think it was probably due to him not sleeping and being in poor health. That was the only conclusion that made sense, it was just a way of showing he wasn't sleeping as nausea is a symptom of sleep deprivation. I think the timing of the scenes just made it look like he was throwing up because of the kissing lol.

Yeah, that part definitely reinforced the idea he's putting on some act. However it could also just be he's self aware enough to acknowledge that he is attractive to the MC, and that there is something developing there.
Tbh because of everything that's happened since that event it's made it hard to think too deeply about it, maybe the author was going to go a different route and changed their mind, it could be to throw people off, it could also be a translation issue. Either way, I think we've gone way past the point it would matter anymore anyway as the MC knows how messed up he is, the cats out the bag.
It's sad to think any sexual interaction between them past this point is most likely going to be rape as MC is doing it out of fear and the plan to kill him. The storyline is so good though, I really am looking forward to where this one goes.
i keep randomly remembering that one scene at the end of chapter 13, where guwon had to puke after his kissing session with the MC. we didn't get a clear answer as to what provoked that reaction. what the fuck was even all of that about?? the lack of answers still makes me a little anxious, 'cause that reaction makes no sense considering everything that happens between them later on in the story and how sex-obsessed guwon becomes.
it was lowkey like a personality switch, or even (and this is A REACH, but) like a different person controlling his body, and he was also talking to himself in 3rd person which on the surface means nothing, is not weird nor unusual, BUT COULD BE intentional, the author has been sneaky with many things here, idk. good writing nonetheless that MONTHS LATER, i still think about this