Honestly, the obsession would have made more sense if he found out about the miscarriage right after asking for a divorce or the divorce finalized. Far enough for him to be satisfied with his revenge just for it to be ripped away when he realized the entire ideal dream life was ruined using his own hands. So kind of like the events make sense but the order that they occur doesn’t?
Also, the concept of him using her as part of the revenge does not make sense to me. In reality, she didn’t actually have anything to do with his revenge outside of him just wanting her to experience the same pain he did. She never took an actions that caused him to want to do that though. No matter how broken he is or how much he begs, he could have conducted his revenge without putting her through that. She told him directly that she was willing to turn her back on her father for him. If regret or reconsideration didn’t even cross his mind at that very moment all the way until well past the divorce, how am I supposed to believe that something actually set off the obsession?
What I'd like to know is what made him become so obsessive about her for real, because I truly don't buy the idea that he just started thinking about her naturally and was haunted by the look on her face when he betrayed her or whatever, or that seeing her name would be enough to trigger this. I get that the point of insanity is that we don't understand how such a person works, but usually you can trace the cause of it at least.
I would also maybe believe he'd truly felt something for Eunyoung if he'd showed some level of regret or remorse while they were together by mutual choice. But you mean to tell me this many who never showed a sign of that during then became haunted by guilt? He himself reflects that he's gotten too absorbed in his revenge game and has actually fallen for Eunyoung, but what part of his actions show that?
Also, perhaps less important, but if I recall, we never really find out what Eunyoung's father actually did other than that it caused Incheol's parents' downfal? Nor do we find out what caused Incheol to react that way to his parents choosing death over him
All in all an intriguing story, but perhaps lacking a fair bit of substance on Incheol's side. Don't get me wrong, his actions inspire disgust and all, but he almost seems like a caricature of a villain with the manipulation, bdsm and sudden spiral into obsession.
But let me just say I appreciate that we didn't get a happy ending after all of that. And I don't think we're going to get any side stories.