Six young women, including Katsuki Takahashi, hold a high school reunion, but their high school has been shut down. The women are happy to see each other again. Suddenly, a shot rings out and one person dies. They receive a text message from Natumi Shirakawa who died 7 years ago. The text message asks "who is the criminal?" To figure out the identity of the perpetrator they look back at what happened 7 years ago.

Girl's High School

Aki  was practically born and raised in a mahjong parlor. At the age of 15, she goes to Tokyo during winter and although she is knocked around by the harshness of the big city, she is determined to survive by the one-and-only weapon she possesses: mahjong. However, standing in Aki's way are unscrupulous adults and the realities of city life.