No he just wants to date joon. Imagine your crush had two choices 1 is you and 2 is another person, you would want your crush to choose you and date your right?
Honestly I think Yoon has suffered enough already and I can see that joon will slowly open up. I know that Yoon didn't go through what joon did but still at least he knows what he did was wrong and he's trying to make up for that mistake while chasing after joon. (⌒▽⌒)
Yes, Yoonseul is making up for his mistakes but he do still has a toxic mindset. Saying Joon shouldn't be doing better just because his confession didn't work out? What did he want Joon to do, just cry for him and be a mess? That's toxic for me, and well maybe it's not for you. And that's okay I guess, this is just fiction.
And it's obvious that Joon still likes him, he's not just that comfortable again being with Yoonseul.
*do still have, I'm not sure. I suck at grammar.
Yes, make him suffer more until he understands that you have every right to date someone else. Make him realize that he has a toxic mindset. (⌒▽⌒)