During her husband's business trip, housewife Mako is asked by a friend from school days to look after her son Shota for a few days. When Mako arrives at the meeting spot, she finds Shota waiting there—the same boy she briefly met as a child. Reunited after so long, they warmly reminisce about old times. However, Shota becomes increasingly drawn to Mako's big breasts, his heart racing with excitement he can't suppress. Soon, he suggests taking a bath together. Seeing a woman's naked body for the first time, Shota is overwhelmed with arousal. Meanwhile, Mako, deprived of intimacy lately and aware of her husband's absence, grows physically sensitive and notices his intense gaze. The stirring emotions between them begin to lead toward a new, forbidden relationship.