My take..

I do agree that Shiwoo shouldn't have tried to make his lover jealous like that but remember that he became messed up after he got raped. Besides, cheating isn't an excuse to beat up and psychologically manipulate someone so badly, it scars them for life.

Well the author did say in the epilogue that Hyun really did have violence tendencies, so yeah fuck him. When was he raped? The only thing I can think of was with that sunbae of his.

He was raped by Mr. Seo that one old dude that wanted to take Siwoo for a drink, touching his shoulder and shit. Then Hyun told him no that wasn’t a good idea but little naive Siwoo still went with him in his car.

I agree. Hyun should've just dumped him and moved on(and if he could find it in himself, then help him?? But he's not expected to really, after being hurt like that...). Being a victim doesn't excuse you from cheating and deliberately hurting your partner (tho it can be explained by psychological behaviour but still CONDEMN ABLE) AND similarly being cheated on doesn't excuse you from assaulting someone for that as well, man it's not worth it.(Tbh we'd all atleast give one hard slap to a cheating partner before finally walking away for good because we're humans and and feel hurt, so if he was only like that then maybe it would've been interpreted as a humane response - tho not ideal, but people are not ideal machines so yeah but mannnnn he literally suddenly turned into a monster and a Sadist??? And it's interesting that you like the character design. Personally Yujin when cross dressing looked really pretty and cute to me haha, nailed it .