高鴨 穏乃

Shizuno is a first-year at Achiga Girls' Academy and the main protagonist of the side-A story. In sixth grade, she met Nodoka and together they play mahjong in the school's childrens mahjong club. She was the club's third best player. When seeing Nodoka's success after she transfered, she makes going to the nationals and playing against Nodoka her goal.

Shizuno is an energetic, athletic girl, and is excited about almost all things. She enjoys hanging out with her friends whenever possible and tries to have as much fun as she can. She become a worthy opponent due to her atittude of never giving up until the very end. When the team falls into despair or is not motivated, she will always step up and cheer them on.

Shizuno seemed to be a typical player with an unwavering determination to win. Even in impossible situations, Shizuno doesn't give up, and is able to count points and account for the other player's habits to calculate her path to victory. However, Shizuno also has the ability to weaken or negate other players' ability, which grows stronger the further the round goes into mountain - the Japanese name for the walls of mahjong tiles. Shizuno also seems to have the ability to nullify player's abilities outside of how long the round has gone on, as towards the end of her match with Oohoshi, Oohoshi started being unable to declare double riichi, despite the fact that declaring double riichi specifically happens at the beginning of the round; in addition to nullifying Awai's double riichi, she also nullified Awai's 5-tiles-from-tenpai starting hands.