Kuroba

Deputy director of the neutral organisation Kotowari.
He is a medical doctor focusing on immunological research, but somehow whenever he sees the protagonist, he can't help but tease her.
He is a good reader of the atmosphere and is everybody's big brother figure who knows how to lighten up the mood, but he is secretly strongly opposed to the colour class system.
He supports Akaza, both as a friend and as a colleague.

In "Catharsis" he is the one who developed "Shirotae", a miracle cure for Haku disease. He is still undecided whether to become the leader of the Yellow.