Ryoko Nagase lives in a rental apartment with her husband. One day, on her way back from shopping, she loses her keys and ends up staying at her neighbor Sayama's place. Sayama, who has lived alone for years and grown lonely, is instantly captivated by the beautiful Ryoko. Overcome by sudden desire, he impulsively pins her down. Unable to tell her husband about the incident, Ryoko is frightened yet gradually finds herself drawn to Sayama deep inside. Later, after being formally introduced to her husband and invited to their home, Sayama reaches for Ryoko's body again. Though her mind resists, her body responds to his forceful, seductive advances. Torn by conflicting emotions, Ryoko struggles with her own desires as she becomes entangled in this new, illicit relationship.