I mean honestly you can't really blame Yoon, for wondering why he got rejected, he got confessed to twice, so he still thinks feelings for him still exist, he knows Joon's feelings for him don't disappear overnight. Yoon, is to blame for the rejection in the first place tho, he did reject Joon twice, while trying to sort out his feelings, why would Joon think he was being genuine? Because that likelyhood is 1 in a million.
