Bum is like 7 years older than Sangwoo so that cqnt be possible
Bum is only 4 years older than Sangwoo.
she still couldve just been with bums dad first then cheated on bums dad with his brother who is sangwoos dad and decided to run away together and leave bum
it wouldnt make sense if they were the same age ( sangwoo and bum) but since bums older than sangwoo it makes more sense if she was with bums dad before sangwoos
oh and
I KNOW THIS IS A LONG SHOT BUT STAY WITH ME NOW
What if bum is sangwoos half brother and the guy the mom was being fucked by in the kitchen was bums father and was sangwoos fathers brother which means there are 3 brothers in total 1) sangwoos father 2)bums father and 3) the uncle that raped bum and all the brothers went to school with the mother and all loved her and sangwoo's father was the one that got her which caused bums father to commit suicide and bums uncle ( which is also sangwoos uncle) to rage in hatred cause he didnt get the girl and was left to take care of bum who looks like the women he loved