During summer vacation, college student Erina returns to her parents' home. Drenched in sweat from the scorching heat, Erina finds out that the bathtub at home is broken, so at her mother's suggestion, she goes to borrow a bathtub at her grandfather's house down the street. Reunited with her for the first time in a long time, her grandfather is overwhelmed by Erina's voluptuous growth, and is unable to suppress the strong desire that has risen up within him for the first time in decades, so he gives in to his urges and attacks Erina. He then takes advantage of Erina's weakness, saying, "In a rural area like this, if even a little word gets around, the mothers won't be able to go outside anymore..."