Nanba is the R.A. of Sano and Mizuki's dorm. He's a nephew of Umeda-sensei, and is one school-year older than Mizuki. He's a "ladies man" although very sensible. He was once in love with his tutor, Kanako Tanabe, but she left him. Umeda claims that this was what caused Nanba to become the "ladies man" he is today. In the future, it is said that he became a model. He, along with the other R.A.s finds out that Mizuki is a girl, but helps keep her secret (although it wasn't a secret for very long). Among Mizuki's group of friends, he seems to frequently butt heads with Nakatsu.
His name is taken from Namba Station, located in Minami, a region in Chuo-ku, Osaka.