I get the feeling he isnt really in love with him anymore. He was in love with the person he thought Sanwoo was which was why he tried to escape and in the begining was thinking of stabbing him. But Bum's situation isnt that good at home either he thinks that he has no where to go and he is pretty scared of Sangwoo still. But I think he is now starting to fall under stalkholm syndrome. In the beginning the 'affection' he showed for Sangwoo felt more like a survival instinct so he wouldn't be killed and since his uncle would rape him he is probably very good at being submissive to prevent his uncles anger. So i think a lot of the initial reactions of Bum to sungwoo were survival instincts honed from years under his abusive uncle.
Actually their is still love, he said himself in one of the chapters. Forgot what chapter but he said it something along the lines of i know shouldn't love him but he does nice things sometimes that makes me still love him. I hate him, i hate how i still love him. Ill agree he adapted survival instinct to survive inside the house, and he tried to escape a few times since he hates the situation he's in. But he himself acknowledged that he still has deep rooted feelings for him.... Bum situation is hate and love, he hate him and yet he still loves him.
The thing is the love Bum had for Sangwoo wasn't a normal type of love that could end in a snap of a finger. What he felt was Obsessive Love. And when it comes to Obsessive Love that Love doesn't end quickly it ends when they find someone else to turn their affection towards. You should remember that Bum isn't normal he himself is one crazy person, that's why his mind cant rap around the idea that "This dude is a monster" he sees it but he doesn't process it well.
YES TRUE
I was recently playing this game called Mad Father an indie game about a girl who was quite aware of her fathers "occupation" of killing people and turning them into dolls. Of course Aya chooses to ignore these aspects because she truly loves her father and believes their is some good in him. In the end, it was revealed she was somewhat psychopathic like him and decides to take over his job by killing people who are illl and turning them into dolls (of course she does it in a much kinder matter *i guess* by making them take sedatives before she kills them to avoid them feeling pain.) I know this sounds like something that should be in the general comments not in the Killing Stalking comment board but i actually though that both the game and the story kind of relate to each other. Bum is aware that Sangwoo is a serial killer but still loves him despite his actions and crazyness and believes their is some good in sangwoo. Bum is also "crazy" (it's probably the appropriate term than psychopathic )but not as crazy as sangwoo. What if in the ending? He decides to escape the house, sangwoo ends up dying but besides living a normal life like most people expect him to do after escaping. He decides to take over Sangwoo "Job" or becomes him in some aspect by also kidnapping and killing people in his house but in a different manner than sangwoo. I though that would be an appropriate ending to this story, something unexpected. :3