Natsukawa

Character appears in the one-shot S no Kaikoroku. He gets forced into being a sadist by his girlfriend. He doesn't want to, but since he loves her, he does it anyway. However, after he makes her bleed by scratching her, he breaks up with her. After another girl confesses to him and they start going out, he unintentionally bit her. This makes him realize he is now a sadist and he needs Sakurai now.