After being cheated on by her husband, Hiroyo decides to separate and temporarily moves in with her sister's family. Though warmly welcomed by her sister's household, Hiroyo's heart remains heavy. When Shuji, her sister's son whom she hasn't seen in years, secretly watches her masturbating, he approaches her that night while his mother sleeps nearby, unable to resist his own desires. Overcome by longing, Hiroyo surrenders to his throbbing cock. This act ignites a hidden lust within her brother-in-law as well. Moaning quietly to avoid waking her sister, Hiroyo writhes in long-forgotten pleasure, taking Shuji's hard shaft deep inside her. That night, a new, turbulent emotion begins to stir within the married couple's relationship.