While visiting his childhood friend's house, Koji accidentally discovers his friend's mother, Reika, masturbating. Having harbored a secret admiration for Reika since childhood, he begins secretly recording her, repeatedly watching the footage while indulging in intense, self-loathing pleasure. But his obsession soon evolves beyond mere arousal, giving way to increasingly twisted emotions. One day, driven by a disturbing thought—believing Reika might forgive him if he showed her the images—he decides to take action.