Yukina felt a deep sense of unease toward her new stepfather. Though she had no choice but to support her mother's remarriage for the sake of their livelihood, she soon realized that his motives weren't rooted in love—but in a twisted desire for her pure, innocent self. As the truth dawns on her, Yukina's mind begins to unravel. Once again, while trying to escape her mother's watchful gaze, Yukina finds herself targeted by her stepfather's sinister plan: a perverse "sex education." Her fragile heart and undeveloped body are pushed further and further to the brink, breaking down under relentless psychological and physical torment.