宮永 咲

Saki is a first-year student and is the titular character of the story. When originally discovered by Kiyosumi's club, she was notorious for her ability to finish plus/minus 0, essentially finishing with the same score she started with (+/- 400 points). When Saki was little, she played mahjong with her family. If she lost, she would lose her allowance, so she learnt how to not lose; if she won too much, her parents get angry, so she learnt how to not win too much. Through this, she developed a dislike of mahjong, seeing it as only a formality for her family to get angry with her.

Her main ability is rinshan kaihou, or winning off of a tile taken from the dead wall after calling kan. It can even go to the extend that she can call multiple kans off of the dead well en route to the win. Outside of using her abilities, her gameplay tends to be rather quiet. However, she appears to get a handle on the flow of any particular game, thus allowing her to make use of her ability.

Saki is a shy, bookish girl with a poor sense of direction. At first, despite her skills, she doesn't like mahjong, in particular because of her family. She is very caring about her friends' feelings, as seen when she loses on purpose to Yuuki to make her feel better and stops doing so because Nodoka says that she cannot have fun if Saki is holding back. Saki gets very excited when thinking about playing against strong competition.

Saki also has the ability to recognize the tiles that can form a kan. She could also feel the fourth tile in the wall one or two turns in advance; when she does this, her eyes wander over to the wall, looking at the tile she can use to form a kan with.