
Kids are just too pure...
Monsters aren't born, they are made.
His parents that made him into a monster he is right now.
Though I wanna happy ending for Sangwoo and Bum,
but I know sooner they'll be punished for the murder.
So happy ending is out of question....
for emotional preparation, I'm gonna hide in the corner and cry.

Sociopaths are made, psychopaths are born. A quick Google search will tell you how wrong you are.

I know he's already crazy, but now that he thinks that bum is also poisoning him and all, so he's totally out of it.
He's thinking that everyone's trying to betray him
So just like that counting the pills in the bottle thing, he probably dropped a nail on purpose to see if Kwak would still believes him or not and was shocked to see that the nail was gone when the old man is leaving.
Whatever, I don't like that old guy in the first place. But still, I don't want any killing scenes at this moment.
I was actually waiting for how Sungwoo gonna fix things up with Bum after all of that harsh words and misunderstanding .
Dammit! It was just getting good and interesting, I was expecting Sungwoo to whisper sweet nothings or apologize or cuddles that cinnamon bun or something. But that geezer just had to come and knocked on the door!! (╯°Д °)╯╧╧
Sangwoo might still hate and wanted to kill Bum till the very last of his breath for he thinks that Bum betrayed him. That's one of the reason to consider why he keep repeating Bum's name on his deathbed.
I think towards the end Sangwoo was going insane and was paranoid. I think he thought Bum was going to poison him like his mom was.
I don't think he hated Bum PER SAY.. I think he just thought he would be betrayed again and want to kill Bum to prevent that from happening. Although we know Bum was just tryna be slick with the rings but hmph...