okay my best guess is that when sehyun said "if it weren't for you, boris might have left that restroom without noticing me" in the ending of the chapter at her grave was because when tracy was being raped by those men, boris saw what was happening to her but didnt do anything he just walked away and didnt help her, and later on she killed herself in the hospital after what had happened to her and in the beginning of the story boris met sehyun in the restroom being done by other men and he was reminded of tracy and thought that if he didnt do anything to stop it then sehyun wouldve ended up the same way tracy did so if tracy hadn't killed herself, boris wouldnt have anything to feel guilty of and wouldve done nothing to help boris in the restroom and minded his own business just like he did with tracy
I'm sorry I wrote so much T~T
can someone recall who’s tracy who sehyun was talking about on ch 61? i’m bad with names (⊙…⊙ )