Кэйко Мисаки

She is Itou's ex-girlfriend and is really beautiful. She used to study at Hibiki's highscool and was Itou's student before. She and Itou began to go out when she graduated from high school but dumps him and begins to go out with another guy. Because of her, Itou's trust for women disappeared and he began to hate them. When she breaks up with her boyfriend, she becomes a student teacher at Hibiki's high school for a short while of 2 weeks. She tries to interfere between Itou and Hibiki's relationship and has them break up for a while; however, she never succeeds in getting Itou.