A family trip to the beach becomes a summer memory like no other. While hiding behind some foliage, son Tetsuro accidentally catches his mother, Mitsuko, urinating. The shock and excitement of that moment leave a deep impression on Tetsuro's mind. From then on, he develops an intense desire to spy on his mother peeing, and eventually obtains a diuretic he finds online. When his mother returns home, he slips it into her drink and maneuvers her into relieving herself in the backyard, chasing that fleeting thrill. The story unfolds in a documentary-like fashion, depicting how a small, everyday incident becomes etched into one's psyche and drives obsessive actions to make it happen again.