Riku Oomi assumes janitorial duties at a remote island training facility after the previous janitor's sudden death. Tasked with maintaining the location used by a girls' swim team and their instructor, he uncovers a hidden collection of video tapes left by his predecessor. These tapes document covert filming activities and the predecessor sexually assaulting a girl in a swimsuit.

Initially disgusted, Riku seals the tapes away. Gradually, his perspective shifts toward sympathy with the predecessor's predatory inclinations. He identifies specific videos featuring swim team members Yoshino, Nagisa, and Matsuri. Choosing not to report or destroy the material, Riku exploits the compromising footage to blackmail the girls into sexual acts, coercively manipulating the situation to fulfill his desires.