APNS-063 I was trained in front of my younger brother... I fell into a masochistic slave... Akari Mitani

Akari works as the president's secretary. One day, her younger brother Shinji messes with a Yakuza woman, and Shinji and Akari are abducted. As a punishment for what her brother had done, Akari was framed by the yakuza. She continues to be sexually assaulted over and over again, and Akari degenerates into a sex slave. Shinji, who saw her older sister acting like that, was excited by her older sister, and she decided that he too would join the Yakuza and participate in her acts.