The secret erotic development of a grandfather who drives an innocent female student crazy - memories of being trained in sweat that summer -

During summer vacation, female college student Erina went back to her parents' house. Erina is sweating from the extreme heat, finds out that her bath at home is broken down, so at her mother's recommendation she goes to the grandfather's house behind the scenes to rent a bath. The grandfather, upset by Erina's voluptuous growth after a long time, is unable to contain her strong desires that have risen for the first time in decades, and she attacks Erina by her energy. He then takes advantage of Erina's weakness by saying, "If rumors spread a little in this countryside, mothers would not be able to go outside..."