Sumire Ryuuzaki

Sumire Ryuzaki is the coach of Seigaku's tennis club, as well as one of the school's math teachers. It was thanks to her that Nanjiro Echizen was able to develop his skills. She is the grandmother of Sakuno. She also has a sort-of rivalry with her ex-mentor, Mikiya Banda a.k.a. Banji, who is the coach for Yamabuki. She is always there to yell, but is also considered to be a great and reliable coach. She has a good relationship with her regulars, and participates in their recreational group activities: the bowling reunion and the beach-volley mini-tournament with Rokkaku Middle School.