The main character offers her friend a job at an unusual cafe. However, as it turns out, a group of villains is operating in the city, who not only kidnap young waitresses, but also subject them to violence.

Hentai tells the story of the relationship between Nanase's sisters Miku and Arisa. They have attractive looks and high intelligence, and are the idols of their school. That is why many young people are jealous of Sosuke-kun, the main character, since the sisters moved to live in the same house with him.