Frankly, i disagree, i think Hoin reacted quite rationally and Chunwoo did what needed to be done.
Chunwoo need to have s** with Taesoo because it's something called closure. It's why when he did it, he saw Hoin and promptly vomited afterwards. That was him realizing without a shadow of a doubt that he didn't feel anything for Taesoo anymore. And the s** didn't happen because Hoin came back, it happened because Taesoo provoked him and then came running back to him, prompting him to finally have a chance to see how he feels. And again, in that moment, he realized beneath all his anger, he didn't love Taesoo anymore.
As for Hoin, he was right to forgive Chunwoo because he knew how mixed up Chunwoo was with Taesoo. He kept being told about it and he made the decision. He knew something would go down between them but If Chunwoo came back to him, that means he chose him, which is what Chunwoo did, He chose him so Hoin made it clear he wasn't going to let him go.
And frankly Chunwoo not being with him does nothing. The main issue was that, they love each other, but one of them is holding onto something they shouldn't, and problem that was fixed by Chunwoo choosing to let go. Now what Chunwoo needs to let go off is his guilt, him and Hoin breaking up wouldn't have done anything.
