i think it’s because he blames him for the death of his brother and that’s his punishment. he’s doing everything that he thinks hyesung wanted to do with his hyung, but since the brother is dead he can’t have sex with him, so he’s giving him “what he wants” as payback for his brother. obviously i’m not justifying what he did, it’s just an inference.
it does make sense but at the same time it doesn't make sense, yknow? it's just... weird thinking that "ah this dude caused my brother to die so I'm gonna live with him and rape him even though I'm straight" but i guess people's train of thoughts are different in the first place
genuine question
why does the brother feels like he has rights on hyesung anyway? hyesung likes the hyung, yet the younger brother was the one being the dick first and told his hyung that hyesung likes men, but then the younger brother feels like he has the right to fuck hyesung? when he was being a dick in the first place? why did he think he has the right?