Doyeon love's Jinjoo, that's for sure. But she's suffering from obsession due to the fact that the woman she fell inlove with was already married. It'll be more easy to judge Doyeon negatively if that's the only issue. But the fact is, that guy is an asshole. He left Jinjoo in a very very dangerous situation that will forever hunt Jinjoo. Those assholes are rapists, harraser, and possibly killers.
While Doyeon, there are so many times when she proves how much she care for Jinjoo. And even some here says that she forced herself to Jinjoo, Jinjoo gave her full consent at first, realizing that she has nothing to lose. And to remind you, Jinjoo is much much older.
It's easy to look at things in black & white, but in reality, things like this happens because of so many factors.
I will not justify the cheating, force sex, and even Doyeon's sour attitude.
My point is, this manhwa is really good, shoving itself to my top 5. It makes me question so many things, and think if the acts were in fact, right, wrong or even justifiable.