While visiting Tokyo for a company training session, nephew Takeshi stays at his aunt Yukie's place. Upon reuniting after a long time, Takeshi is surprised by how much she's changed. With age, Yukie's figure has matured into a more refined, distinctly adult allure. The next day, while cleaning Takeshi's room, Yukie discovers her own underwear beneath his pillow. Realizing he had been wearing it, her hand instinctively moves between her legs. That night, she visits Takeshi's room braless, guiding his inexperienced hands toward her full, soft breasts. From this moment on, their relationship takes a new turn.