At a mixed-gender hot spring, unfamiliar men gather and begin playing pranks on the reluctant Marichan. Her boyfriend, a major sadist, might be eager to show off his cute girlfriend. Though shy and embarrassed, Marichan's pussy steadily gets wet, growing more aroused from being watched. Forced into a wide M-shaped spread, she's made to masturbate, perform blowjobs, and even take cock into her back hole. The rhythmic "slap, slap, slap, slap" echoes throughout the bath, creating an atmosphere like a special performance.