This is a sequel to the previous three works but it has been written so that it can be enjoyed as a standalone story.
"Make me your flesh toilet." At the request of my childhood friend Mitsushima Hitomi (Hi-chan), who attends the same school, I, Sanada Yuto (Yuttan), took her virginity in a filthy park restroom and began treating her as my flesh toilet. In the restroom, in an empty classroom and behind the school building.... This lewd relationship repeats itself almost daily. Despite their promiscuous sex lives, the two have feelings for each other. "No one will be home until late next Sunday." When I visit my childhood friend's house for the first time in years, I find Hi-chan (Hitomi) there, dressed in her sexy casual clothes... While spending the time together under the pretext of reviewing for a test, memories from my childhood come back to me and Hi-chan seems strangely close to me. Yutan reaches his limit with her overly expressive behavior... And what will the future hold for their relationship?