Responses
Honestly think the puking after kissing was just him not getting the sensation and it being gross to him but him not complaining or saying anything because teach wanted to do it and he doesn't seem to really know how to say no to teach. Ever since the chapter where teach affirmed his feelings and also convinced him to sleep, he's been really into kissing probably because it finally clicked for him the appeal.
I'm convinced Guwon isn't even one of the undead, but more like the first one? And that's why he's maybe more conscious than other maggots would be? Sisyphus himself, in a way, balancing the stone, cheating death. Also we've never seen him eat.
Maybe the puking after the kiss has something to do with that, since he technically swallowed someone else's saliva? Or maybe he's just an asshole haha