One afternoon after school, second-year middle school student Aoi finds himself alone in an empty classroom. There he encounters a mysterious girl with striking blonde twin-tails, who is quietly giving in to a private, urgent impulse. Her name is Bambi. What begins as an accidental shared moment quickly becomes a mutual secret: the two agree to become exclusive partners in a hidden act they call their secret impulse. They turn a disused former photography clubroom into a secret base where they can indulge their desires away from prying eyes.

As their relationship deepens, Aoi and Bambi navigate the awkwardness and excitement of adolescent curiosity. Their bond is tested when a second twin-tail girl enters the picture, introducing new dynamics and complications. Aoi also experiments with cross-dressing, further blurring the lines of their hidden world. The story unfolds in a middle-school setting, focusing on the pair’s evolving emotional and physical intimacy, the thrill of shared secrecy, and the growing question of what their connection truly means beyond the physical. Blending romantic comedy with ecchi elements, the series follows their journey from mere curiosity toward something more genuine, all while they struggle to keep their private world separate from everyday school life.