I don’t understand. Just…why…? Like, was it really necessary? I thought that Yujin ...

Yujin has insane trust issues because of his dad you see it in the whole “I love you” part, if the man who was meant to protect you from all harm is the one who A) harms you B) harms the man you LOVE (because by this point it’s clear Yujin loves Aaron) then obviously a man of such a status as Aaron will abandon you (or so what Yujin thinks). It’s only natural for him to run because that’s the only thing he knows, whether he does it to protect himself or Aaron? Up for debate.