Sayoko Miyamura is an exemplary student, well-liked among her peers, and often the center of attention in social settings. One evening, as she walks home alone at night, Eto, who harbors feelings for her, witnesses her being pursued by a group of men. Despite his initial reluctance to intervene, he musters up the courage to grab her arm and save her from danger. However, upon closer inspection, he realizes that this version of Sayoko is vastly different from the one he knows from school. This new persona, known as 'Yoko,' possesses a rebellious demeanor, a foul mouth, and an insatiable sexual desire.