Running a small town factory with her husband and a handful of employees, Yumi spends her days working tirelessly from morning until late at night, busy on the shop floor. Recently, her son Satoru has started helping out at the factory, strengthening their family bond. However, the two have secretly begun a forbidden relationship, making love without her husband's knowledge. Driven by the thrill of secrecy and the fear of being discovered, their illicit passion intensifies. Amid the routine of daily work, hidden emotions begin to surface, drawing their hearts closer as they pursue the forbidden pleasure they share.