(incoming spoilers)
basically, juyeon really tortured jiwook each time he "misbehaves" (it gets worse each time) then one day while juyeon went out to visit his mother, jiwook tried to escape with the "help" of suhyeok and ofc it goes all bad; this is also where juyeon unravels and gives us a backstory as to why he's even doing this to jiwook. apparently they met when juyeon was a middle schooler and developed feelings for jiwook but jiwook did not take that well and was homophobic, then one day jiwook and his group decided to gangr*** the 14 yr old juyeon, and jiwook doesn't remember that at all. so after the failed escape, juyeon brings both suhyeok and jiwook to a sketchy torture warehouse and reveals what happened that time to suhyeok who was bound, and juyeon also gathered different people/thugs that jiwook fought before and made them do what jiwook did to juyeon before. so after that, juyeon brings jiwook to the hospital and jiwook vaguely remembers what he did to juyeon, and while they talk jiwook reveals that he DID like juyeon but has internalized homophobia (jesus christ) and jiwook has been successfully made super dependent on juyeon so boogsh they still end up and live together (jiwook still assumably on a leash and forbidden to interact with the outside world)
Yes, back in highschool days, Jiwook likes Juyeon, but it's just because of his face, he's a sucker for pretty faces (even now and after), Juyeon adore Jiwook, he think he was cool and very handsome (No, realy, Jiwook is literally a poster boy in his uni, he was called as "a trash with a pretty face").
And about the extra story, man, that's where people start to think the revenge is only an excuse for everything that Juyeon did. More people hate Juyeon than they do with Jiwook, there's beastality (got revised), mind breaking of no return. They once pitied Juyeon, but then it's just...died of heart attack sound like a heaven's mercy for Jiwook.
They looks exactly of how they're now, but younger. Juyeon with his pretty face, and Jiwook with his handsome face. And no, Juyeon didn't tell anything even till the end, it was Jiwook who remembered their past. It was when Jiwook got brutally gang raped again until he ended up with broken bones, ruptured organs, damaged urethra, and so on, simply couldn't function anymore. He remembered everything (or just bits, idk) on the final main chapter.
Are we near end? Maybe in another 40 chapters again? The main story is in the 65%ish rn.
Well, if what Jiwook gone through is merely a karma of his actions, why there's a debate of Juyeon's actions ? It should be just deserved right? Deserved, end of the debate.
But no, the truth is the revenge was done , it should be ended in this red room, cause this is the amount of sins Jiwook has comitted, if it was only a revenge, then it's enough.
Well, things got much worse for Jiwook. The people in the Light Novel comments start to pitty him, and screaming over and over, it's enough, the revenge was enough. The second gang rape with all that wounds is more than enough.
The extra story is only the author's fetish, revenge is only an expired excuse for whatever tf happened later.

yeah, i guess they belong with each other jesus christ