I feel like Kinn still didn't forgive himself for what happened in episode 4, he didn't kiss Porsche during his…
I rather think it's his father's fault for putting pressure on his relationship, Kinn wants/needs to obey him but he finds it hard to fight the feelings he has for Porsche. Finally he does not resist when Porsche confesses his feelings to him.
I hope he dies at the end, that's all he deserves.