Three years into her marriage to the second son of a family of three brothers, Rio lives with her husband's family. Rarely touched by her husband, she finds solace in loneliness through masturbation. However, when she accidentally sees her younger brother-in-law's naked body emerging from the bath during her husband's week-long business trip, her suppressed desires explode. She pleads with the younger brother-in-law, but her older brother-in-law catches them in the act and begins secretly watching their encounter. Just before an important party they had previously planned, the older brother-in-law makes his move...