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, Shinji's younger brother Shinji hooks up 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. After being sexually assaulted over and over again, Akari degenerates into a sex slave. Shinji, who was watching his older sister like that, gets excited about his older sister and decides to join the yakuza himself and participate in the act.