Ishimori Uka is very shy and has a hard time making friends. When she was a middle school student, students made fun of her by calling her "stone". Around that time, she met Miura Kai with lemon color hair. Because of him, she entered the same high school. Uka now wants to overcome her shyness and have friends. Kai is a popular student at the school, but he doesn't talk much or seem interested in others. He doesn't know why, but he becomes concerned with Uka. Uka has admired Kai, and she now has feelings for him. Kai has a secret, which no one knows.
Hazuki and Aoi are classmates but their relationship outside class is fraught, and outside school non-existent. But when both girls are drawn to helping an elderly woman, they're forced to interact, confronting their differences and similarities as well as their deepest secrets.
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.
Akari Inui and other students are kidnapped and imprisoned. They are forced to take part in a game to kill and survive. The last survivor will receive one hundred million yen.
