
As much as I hate Woojin for cheating, his mental state isn’t something I can hate him for. After thinking about it, I kinda change my mind, I would probably still be with Woojin if I were taehwan, instead of breaking up, I’d try to get him to open up gradually, then tell him that he’s being abused and manipulated by that ex of his. We’d go to therapy for him long term, then if he does improve and does his best to try improving, the relationship can definitely work out.
But of course it’s up to Taehwan. He’s been hurt before and now so it’s up to him really. It can be hard when your partner is manipulation prone and such.
Knowing Taehwan, I’m sure he will understand later on if told.
Even if this is Woojin is being blackmailed, he's the one that brought this situation upon himself. Telling Taehwan would've been a better scenario than the constant cheating he will to afterwards just to protect himself and Taehwan (from finding out).