I'm gang-raped by my son's classmate every day.

Sayuri lost her husband early and raises her son, Takeo, on her own. Takeo had no particular rebellious period, and Sayuri was modest, but he thought that this life would last forever... However, one day, a man named Koji, Takeo's classmate, comes to his house. Koji, who had been experiencing trouble with Takeo and his female relationship, had intense hatred towards Takeo. And that day, Koji returns home without doing anything, but the next day he shows up with his bad friend to Sayuri...