While tutoring his friend Kasai's girlfriend, Kyouko, Segawa finds himself the target of her aggressive seduction after Kasai leaves them alone. Kyouko reveals her frustration with her boyfriend's selfishness in bed and lures Segawa into a passionate affair. As Kyouko continues to seek pleasure with other men, it becomes evident that she thrives on the thrill of infidelity and the feeling of being "tainted."