Miyanaga Saki is a first‑year high‑school student who has learned to play mahjong in a unique way. Her family is furious if she wins the household tournaments, yet losing is also frowned upon. To balance both expectations, Saki develops a special strategy that keeps her score consistently at plus‑minus zero, a near‑impossible, almost perfect result in a game that relies largely on luck. Though she has always disliked mahjong, her middle‑school friend Suga Kyōtoro insists she join the school’s mahjong club. With her refined skill and extraordinary luck, Saki quickly becomes a formidable opponent, even capable of challenging the middle‑school national champion.