Where did the author foreshadowed it?
Both the parents died and that bum and sangwoo are like re-living the two characters. It's like a twisted cycle
holy shiz you right. as much as i want a happy ending it just wouldn’t fit for this.
What Yamete, oshiri ga itai (lol @ your username) said is true
Also, in Chapter 53, Sangwoo asks Bum to promise him to "Die together" if Sangwoo dies first, Bum should slit his wrists/die with him
what if sangwoo kills bum, and after he kills him while he's cleaning the house he goes into the laundry room, and discovers the unused pills under the shelf. Figures out that Bum didn't want to kill Sangwoo, and realizes what a huge mistake he made. He, then, starts to investigate what Bum was going out and using money for, probably something to help Sangwoo (maybe he was working to buy a gift for Sangwoo, or trying to buy medicine for Sangwoo, maybe a house since Sangwoo's current home reminds him so much of his parents and his trauma...idk). Realizing there's no going back, Sangwoo ends his life.
In the meantime, the police figure out Sangwoo is a serial killer, go to check his place but discover no one is home because Sangwoo/Bum are dead.
If not, then Sangwoo hands himself over to the police, goes through court, and is either locked up in a mental hospital or jail. But this is somewhat unlikely. I have a feeling this story will end in a double suicide/suicide-homicide because the author already foreshadowed it.