Toki Onjouji is a third-year student at Senriyama Girls' High School in North Osaka and a supporting character in the spin-off manga Saki: Achiga-hen episode of side-A. She was named one of Senriyama's ace players for the 71st Inter High School Mahjong Tournament despite being a relatively unknown player prior to it. Toki is physically weak, she is constantly being cared for by Ryuuka. Though she cares for Ryuuka and other members, she doesn't want to become a burden to them as she is always being hospitalized.

Toki possesses the ability to predict one round of discards accurately, allowing her to call a riichi immediately prior to it to take advantage of the win bonus. She also rarely calls "riichi" because she wants to hide her "tenpai" from opponents. She also has the ability to see two, and even three turns into the future.