I was wondering the same thing. But sometimes relationships don't develop between two people or feelings either. Maybe the side character realized that he would never get the attention he was looking for because he was never brought up by the main character anyway about what happened. Sometimes things like that happen in real life, person likes you and kisses you but you don't say anything about it because it doesn't matter because you're not even interested and you just carry on with the person you're with. No sense in bringing it up no sense in just starting drama that don't even matter.

this story was good but what's the point of that side character kissing wushin