I feel like chulsoo has too much of an obsession with someone who just does not reciprocate at all. I get he did that out of love, but it was wrong, and the fact that she had a boyfriend when she started to experiment... it's just really messed up. she should have talked to her boyfriend and figured things out if she was that pent up.
I believe she had already started experimenting before she started dating Jiha. That's what was implied in the rumors in the flashback with the high school reunion.
Hahahahahahaha almost died laughing. This is what I call yaoi taken to the extrem