Zero (a.k.a Furuya Rei) is only in the Black Organisation working undercover as a Security Bureau Officer. He only hates Shuuichi Akai because of a misunderstanding, yet Akai decided to leave it at that and now Rei thinks he is the cause of an event and so, the extreme hatred for him. But, other than that, he is a good guy as he is only putting up an act.