idk why but i have a feeling the real psycho was the mum...and he said it cos he doesnt want to be killed by a crazy woman like his dad.... that is why he is able to be soft at times towards Bum..cos he is a boy..and that also explains the his hatred towards the women....she must have put a lot of trauma on him cos he is always putting the women he is killing into the role of his mum.. (you could saw it during the ski trip) i think he is keeping Bum around cos having a person who blindly is caring for u keeps him to feel like he is still not that huge of a monster... i also think he got even posessive over Bum and is taking him as more of a property...(explains why he got so jealous over the fact the uncle raped Bum to the point he had to kill him) That´s why i dont think Bum represents the mum cos if he did...he would already been dead... ╮(￣▽￣)╭
This^ is a good theory and makes sense.
He was saying that he didn't want to end up like his father... but which part? Beating and hurting the mom? Crazy? Dead like that? Or other thing that was not mentioned yet? In my view, Bum is the "mom" and Sangwoo dont want to be the "dad"... I dont know, it's so hard to conclude something (￣ε(#￣)Σ