
It's called "Love or Hate", which reflects Haesoo's feelings towards Joowon throughout the story. It was never actual hatred but rather a deep feeling of frustration and loneliness which at times was akin to hate. Simultaneously he craved his touch and being in his presence. The whole time he's been trying to figure out the true nature of his feelings for Joowon (love or hate).
On the contrary he never felt "love or hate" for Taku. Their relationship was pretty casual and uncomplicated (until Taku somewhat made it so towards the end). So from the beginning I've always been 100% sure that Haesoo and Joowon were endgame because the story was always about their journey.

It's a thing that happens in real life. Some men rape gay men to make them "understand" that gay sex is painful and unnatural. It's a form of punishment, a way to chase the gay out of their bodies. Of course it's wrong, disgusting and sick but some people are litteral demons.
So if Seungho was raped as a child then I can totally imagine it unfolding like that. He did say that he's living by "the principles father taught us" when he spoke to his little brother. Maybe he was alluding to that? His dad allowing old men to rape him, except Seungho as an adult turned the tables on him by willingly engaging in gay orgies just to rebel against his dad and also as a way to relive his trauma (many rape victims do that).

Yeah. I did wonder if childhood abuse and trauma were risk factors or linked to it but then I got sidetracked and forgot. Lol. After your reply I had to look at the chapter again. So if the original "illness" was homosexuality that Jiwha "caught" from him as mentioned, I guess Seungho and Jiwha were found doing something together which lead to Seungho's confinement to his home? And then abuse like what you mentioned or some other physical/emotional abuse from his father occurred either before confinement or after. I'm kinda unsure of the timeline on the events described in the chapter. But...all I'm gonna say for sure is that there was some depression going on years after the abuse since in the scene of the doctor's second encounter with him probably suggests a suicide attempt where there's a knife on the floor. On top of the other self-destructive behavior of drug and alcohol use, impulsive sex and then what the doc described as delirious fits and insomnia. So I agree. Maybe bipolar disorder or even PTSD and comorbid depression or bipolar disorder and PTSD. With your theory and everything else; that is seriously some complex stuff to be alluding to. And a lot of it. But I guess we'll just have to wait and see.
OMG CHRISTMAS CAME EARLY