Even though she looks like a child she is a famous lead singer of a music group as well as the head of the music club. Koume initially disliked Yamato but started to soften up when Yamato dove into the swimming pool during a competition to save her. She developed a temporary crush on Yamato which partially faded when a university student protected her from a pervert. She eventually starts dating Tamanami Youji who is part of Yamato's boxing club. She also has the habit of saying Myo like a cat.