While his wife is away at her parents' home for childbirth, her older sister, Kyoka, begins helping out with housework. Overwhelmed by the demands of work and household chores, Kenji happily welcomes Kyoka's assistance—unaware of her true intentions. As he focuses on cleaning, Kyoka repeatedly initiates excessive physical contact. Flustered, Kenji tries to pull away, but she chases after him, whispering provocative words that stir his emotions. Her bold actions gradually disrupt his everyday life, igniting an intense and forbidden desire.