In a corner of a downtown neighborhood stands "Wani no Yu," a public bathhouse beloved by locals since the postwar era. However, with modern homes now commonly equipped with private baths, the number of visitors has steadily declined over the years. In an effort to attract new customers, the owner hires Hitomi, a married woman, to provide a special service called "scrub massage" inside the men's bath. Shy and flustered at first amid a room full of erect penises, Hitomi continues her scrubbing duties. But as time passes, her sexual frustration grows and her body begins to ache with desire. As she scrubs each man's body, she eventually comes into contact with a large cock. In that moment, how will her mind and body be shaken?