Sister Mirai (25), an office lady, is lively and outgoing in her private life. Her younger brother Masaru (24) is a freeter, and the two share a close bond. They challenge themselves with a unique game of strip baseball. Masaru acts tough, saying "There's no way I'd get turned on by my sister! w," but his reaction only adds to the excitement. Mirai has a pure, cute face, smooth skin, large breasts, and a body that looks great in a high-quality bikini. Faced with his sister's alluring appearance, Masaru gradually becomes aroused, eventually getting an erection so strong he feels embarrassed. As they continue stripping each other, their playful banter gives way to increasingly passionate action. Suddenly, the scene shifts into deflowering incest play.