After years of enduring abuse from her mother-in-law, Minako accidentally injures her during an incident and, overwhelmed with panic, flees her home. She assumes a new identity as Marina Matsumoto and begins working at a factory, laboring alongside male workers in grueling physical jobs, hoping to live a quiet, stable life. However, when a detective arrives searching for her, she is discovered by fellow worker Fuchigami, who seizes the opportunity to blackmail her. To keep her job and hide her past, she is forced into degrading anal training and gradually reduced to a sex slave, used by the workers to satisfy their base desires.