A 1.ª temporada de Immoral Sisters estreou a 27 abril 2001.

A sincere older step-sister and a curious younger step-sister are doomed to become love slaves. One day, a house wife named Yukie has a traffic accident. She is ordered to pay a large settlement to the other party, Taketo, the son of the owner/president of Nogawa Industries. Unable to make the settlement payment, Yukie allows Taketo to have her sexually. At the same time, Takato's father, Nogawa, approaches Yukie's step-daughter, Rumi, and blackmails her. His evil scheme even reaches for Tomoko, Yukie's younger step-sister.

A 2.ª temporada de Immoral Sisters estreou a 28 fevereiro 2003.

Taketo returns for another competition with his father to see who can bed Yukie, and as many members of her family at one time and how often. Will they be able to call a truce, or will the sisters be caught in the crossfire? And when Yumi, his father's secretary, gets in on the act, a six-way is inevitable.

A 3.ª temporada de Immoral Sisters estreou a 25 junho 2004.

The sister of Miyatsuji Kotono and Suzuyo went to the Ikaruga High School where her mother Kasumi acted as a leader of the trustee. The two beautiful girls adored Kaneshiro Shoichi. However, he gave his concern only to the school doctor, Morisawa Maiko, and he was captivated by her body.

Because he would be expelled from school if he didn't pass the examination, he was tempted by Maiko to break into the principal's office, and stole the disk that contained the examination.