When his father remarried, Kaori became his stepmother, and Ataru, his step-son, secretly had feelings for her. Although he was his stepmother, Ataru tried not to show his feelings towards her, but he relieved his stress by secretly filming her. One day, Ataru witnesses Kaori masturbating at home. Excited, Ataru secretly films her and is about to look at the footage in his room when Kaori comes into the room...