The granddaughter of [Sumire Ryuuzaki](https://anilist.co/character/9489/Sumire-Ryuuzaki) _(the Seishun Academy tennis coach and math teacher)_.

Sakuno is a kind, nice and quiet girl who almost always seems to worry about [Ryoma](https://anilist.co/character/324/Ryoma-Echizen) and the others. She started playing tennis after she saw Ryoma playing, and her progress differs in the anime from the manga; in the anime her lack of skill is a recurring gag, while in the manga she's good enough to be seen as a promising player and even a future regular. She even received a Certificate of Commendation for ranking 3rd Place in the Women's Division, as stated in Pair Puri.

In both the anime and manga, Sakuno's crush on Ryoma is clear, she hasn't had a chance to really tell him due to her own shy nature, some degree of bad luck and the meddling of other people _(especially Nanjiro Echizen and Takeshi Momoshiro, and occasionally Eiji Kikumaru)_.