Nanako starts living together with the intention of getting married. Her close friend's younger brother also lives with her. One night, she allows her body to be violated by his younger brother... "Forget about this." They both share the same desire not to make their boyfriend sad, and try to end the relationship, but her brother, who has fallen in love with her for real, violates her again. Nanako knows it's wrong, but she is brought to orgasm by the intense sex and Nanako into depravity. The two, who should never be connected, repeatedly devour each other raw, cumming inside each other...