The Uke took responsibility for cheating, the other person didn't take responsibility for lying about who he was, what he was, why he kept disappearing (Ghosting) on some one he's supposed to love, and even his relationship status (dude had a secret fiancé he was technically cheating on). Honam was also not really treating him like a person and honestly can you even say that he was in an actual relationship with Honam by the time he slept with his boss? I find the argument that he cheated kind of laughable because at that point it wasn't really a relationship so much as a haunted ship with a Ghost that pops up every few weeks and a Uke sailing in dangerous waters alone while being spied on by minions of his ghosty.
Also he was pretty very drunk and emotionally broken when he slept with the not drunk Boss. Which would make that incident rape by my book. BTW getting raped is not cheating. The fact that his rapist was a better guy than his current BF says a lot about that bf. Also he didn't blame his cheating on Honam he blamed the break up on Honam's actions. I do wish he had the break up talk before he slept with the other lead though, and that they slept together with less of a dubcon situation but hey progress, the uke ditched the toxic ex in the story instead of sticking with the first lead no matter how toxic they where. Seon made a healthy choice to break it off and another separately healthy choice to pick a guy who was treating him well.
First he cheated on honam and then blame him even if he was heart broken its doesn't mean that he should go and find someone else. First he should clear the misunderstanding. ACK!!! I feel so angry.