I kind of just attribute it to his emotional maturity at that age and that Taegun was his first love. That's what first loves are, you don't know what you're feeling and you're unsure most of the time, you're wracked with nerves that you'd mess it up. What more of Yonwoo who was close to Taegun most of their life?
I think Yonwoo himself understands that what he did was horrible but he probably reasoned in his head that it was better to leave than receive Taegun's outright rejection. It could be self-preservation but also cowardice (they are not mutually exclusive). The time did them some good though, bc they already had a solid idea of what they really wanted from each other after all the misunderstandings were solved. Most relationships irl don't even have that lol.
But I decided to restart it. I’m at chapter 3 now and I figured out what the thing was that bothered me about Yoonwoo’s character. It’s the fact that he knows (in his mind) that if TG finds out he’s an omega he’ll distance himself from him but that’s literally what Yoonwoo did. You reject/distance yourself from him first to save yourself from being hurt but the whole time you’re miserable? How is that any different? If anything it’s worse to distance yourself from someone as close to you as family with NO EXPLANATION vs someone distancing themselves because of trauma.
Just to be clear I didn’t stop reading this because I didn’t like it, it was just something nagging me about his character that I couldn’t put my finger on it. I’m going to finish it now lol.