Mahiru, a female college student, begins a new life with her stepfather after her mother remarries. Mahiru has come to Kokoro her very kind stepfather, but one day, everything changes. She witnesses her stepfather devouring Mahiru's underwear from the washing machine. However, she doesn't want to see her mother sad. From that day on, Mahiru distances herself from her stepfather, but her grandmother falls ill and her mother has to go back home for a while. Then, when Mahiru tries to escape to her friend's house, her cunning and perverted stepfather gets in the way...