Hisae was asked by her younger sister, Kyoka, to take care of her nephew, Kazuaki. Kazuaki is a pure, inexperienced boy who has never been with a woman, and reacts innocently whenever Hisae exudes even a hint of sensuality. His innocence excites her, and out of boredom, she invades his bathroom while he's bathing. Though confused, Kazuaki gradually grows aroused and tense under Hisae's touch. His cock is playfully manipulated, engulfed in pleasure he's never felt before. Soon, guided by Hisae's hand, he reaches climax and ejaculates. Yet Hisae's desire remains unsatisfied, driving her to go even further and push him deeper.