One day, Shiori, an honor student, visits the home of her shut-in classmate, Eusei.She was greeted by her father Koji.At first glance, he seems to be a kind middle-aged man, but in fact he is a former yakuza, and has been involved in various behind-the-scenes jobs.The bookmark passed through the eugenic room is circulated by eugenics and Koji.Eusei was also a collaborator of Koji and others, and she didn't go to school because she enjoyed such acts.I can not resist from fear, I will be left as it is, but gradually masochism will sprout ….