Responses
That's exactly the problem. He doesn't feel sorry because he intentionally hurt the person he now loves only to entertain himself, he feels sorry for himself because he can't get what he wants.
It's always the same. The reader is supposed to forgive the prick because the prick suffers instead of showing us a scene in which they truly regret what they did because they realized how despicable their actions were. They just regret it because their behaviour hurt themselves.

Honestly, the whole time Kou was getting sick I was laughing. Fuckin prick. Oh now you're sorry? Such a shitty person. He doesn't even regret being a bitch because he hurt people, he regrets it because it ended up hurting him.