Responses
I think is gonna be something like this, I like your theory it makes sense
Slight spoiler//
I think this is actually what happens. I remember seeing raws a few weeks ago and I can't understand Korean so idk the dialogue but I think it's very similar to your theory
updated my theory: so taehwan has a trauma from being bullied at the boarding school—you know the sexualisation of asian men and that whites like to say we have small dicks or whatever? taehwan being one of the few (probably) asians in that school was probably picked on using that excuse or/and that he was too feminine for some reason. or! everyone said that he was gay for some unknown reason regardless of whether he actually was (the horror,,, maybe calling slurs & aggravated the bullying)
thus, as an impressionable young boy, knowing the consequence of being associated with the word gay, taehwan started associating being gay to being filthy. his internal homophobia is off the charts too,, yeonwu seeing him kissing the girl could be evidence that taehwan’s bi or it could be him forcing himself to protect himself from rumours etc.
oh ++ adding to that, taehwan could have been sexually harassed or, at worst, assaulted; which is why he reacted so strongly when yeonwu kissed him in his sleep (which is noncon btw).
tldr: taehwan trauma therefore he’s particularly prickly about consent + the explanation for his internal homophobia
ALSO POWER BOTTOM YEONWU TOP YEONWU SERVICE TOP TAEHWAN