Coach Ryuzaki is the coach of the tennis club. She is described as 'Grandma' by Guo Yu after he accepts her candy. She is gentle and understanding, insisting that 'rules are dead, but people are alive' when Tezuka hesitates to let Guo Yu into the tennis court. She gives Guo Yu candy, which changes his address from 'Grandma Ryuzaki' to 'Grandma'. She hopes Tezuka can relax and not carry all burdens alone. She is caring and approachable.
