The series 'Shakkin Shimai' follows the tragic story of two step-sisters, Ayano and Misono, who are plunged into a world of sexual depravity to pay off their father's massive debt to the yakuza. The loan sharks seize their home and force the innocent sisters into a relentless series of hardcore sexual encounters. The narrative chronicles their forced degradation as they are passed around and used by various men. Ayano, the older sister, is subjected to brutal gangbangs, her orifices relentlessly pounded and filled with cum. Misono, the younger and more naive of the two, is deflowered and repeatedly raped, her tight, virginal body stretched and abused. They are forced into performing deep throat fellatio, getting cream-pied, and enduring intense anal sex, all captured on camera to be sold as pornography. The series depicts their complete submission and the breaking of their spirits as they become nothing more than cum-dumping sex slaves for the yakuza's pleasure and profit.