All these people? It's been 3 relationships that we've seen and one of them begun in high school. I don't see this glaring "something bad" that Si-Eon is perpetuating in all his relationships? He gives his partner free rein to choose, moreover his relationship with Namwoo began transactionally. In a relationship Si-Eon is only responsible for HIS own feelings, and he was very clear what was possible for him and what wasn't. That Namwoo chose to proceed anyways was entirely up to him, that being said however, it's unfortunate that they ended up not being on the same page. He's not lying about being in love when he's not (he learned from the high school ex) Growth isn't linear clearly, but he's not some fuckboy jumping from partner to partner leaving trauma in his wake either. His female ex is clearly capable of functioning in a romantic relationship after him, so really... Where is the debilitating "something bad" he's inexcusable of?