Sangwoo is going to kill Bum. I said it before and I'll say it again, the only reason I think Sangwoo killed his mom is because his mom, after blurring the lines of their relationship, "cheated" on Sangwoo like she did with his dad. I believe this is why we see the contraceptives with the rat poisoning. He might think Bum will do the same thing? Also, did Bum just ask that girl for runaway money? Awwwww shiiiii.
Because Sangwoo had switched them those years before.
Also, I was right... Sorta...
http://www.mangago.zone/home/mangatopic/3523013/
Side note: I think Sangwoo's mom coerced him into romantically falling in love with her over the years. I think maybe his dad and she were fighting that day because his dad found out that she poisoned him. Sangwoo intervened and it was the finishing blow. After he died, I think she still cheated around with other guys so Sangwoo, being romantically in love with her, killed her. If psychopathy is inherited, he got it from her.
Js. Either or would be hot.