
I mean but it was obvious Dohyun was an asshole. Sungho was too blinded by his desperation for a friend that he knew deep down wasn't going to return the same feelings. It was 100% Sungho's fault for putting himself through his crappy past with Dohyun (he had the choice not to). I understand the desperation to want friends all too well but I also know not to be friends with someone who won't treat me right. Sungho has psychological problems. He was searching for too much from school mates and he didn't know what to do with his strong feelings of obsession and infatuation.

You have good point, Dohyun is an asshole and Sungho had the option to say no and walk away but didn't, so the whole grudge thing is not going to resolve anything between them. All this kidnapping, violence, and rape just shows Sungho is mentally unstable person who doesn't understand the difference between love and obsession.
Dohyun did all those horrible things to Sungho, and Sungho stayed because he didn't want to lose Doyun but it's obvious that he just want be friends with him but Dohyun wanted a "different" kind of friendship. Man, this some pretty fucked up shit ain't it?☹