Momoka lost her parents, dropped out of high school, and raised her younger brother alone. However, her younger brother applied for a part-time job without knowing it was illegal, and was being threatened by a group of semi-criminal gangsters. When she went to apologize with her younger brother, the leader, who fell in love with Momoka's beauty, offered to forgive her everything on the condition that she be his mistress for 10 days, and Momoka accepted his request... The leader's sex was rough, and he was sadistic, treating women as a means to satisfy his sexual desires... However, the carrot and stick, and the rough treatment he used, gradually awakened Momoka as a masochist...