Yami-ma no Mamiya begins its story in the Reiwa era, 20 years since the death of the legendary mahjong player, Akagi Shigeru.

They share with Osamu that they are massively in debt to an entertainment producer named Onigashira Kanji, and that a single mahjong match with him could earn the young men their freedom, with the help of Mamiya.

After a period of rough plays, Mamiya finally arrives to replace Osamu in the battle against Onigashira and reveals herself to be a precocious teenage girl.

In an attempt to provoke Onigashira, Mamiya bets her virginity as stakes in the gamble, and the two set off in a match of "Yami Mahjong."

Fukumoto published a "chapter 0" in Takeshobo's Kindai Mahjong on May 1, 2019;[2][3] it debuted as a serialized manga two months later in the same magazine on July 1.