Responses
- Maybe the mother told her son that she was entering a suicide pact with her husband, as dying together was an act of love. But this turned into a murder (dad) suicide (mum) pact instead, seeing as there is a flashback of the dad running away from them?

Questions
- Was that Sangwoo's dad with the mum in the last bit? If so, do you think this was her way of fucking with her son who knows she's cheating, and is jealous that her son loves his dad by "showing" that she still loves her husband, and as a way of scaring and sexually abusing he young child by making him witness them?
- Was the room in question, the same room at the start of the webtoon when Bum breaks in and fantasizes about Sangwoo, on the mattress that was still there? Isn't this the room that has the trap door which leads to the basement which is where most of the crimes have taken place? I think if so, this location might be relevant to more of Sangwoo's backstory and his parents deaths.