Shota, living in an apartment complex, had recently been experiencing discomfort in his groin, making life physically and mentally tough. One day, Yui, a girl aiming to become a gravure idol, moves into the neighboring unit. She's a girl with a pure vibe, known for her thick thighs and large, shapely butt. Shota becomes obsessed with her backside and decides to play a prank on her. His friend Taro gets dragged into it, and the two of them corner Yui for an intense butt-focused tease. As their relentless teasing continues, Yui gradually grows aroused. Her sexual desire builds steadily, eventually pushed to the brink of explosion.