Ruka's uncle and his son Daichi come to visit her house for the first time in several years. That night, Ruka's uncle invites Daichi to take a bath with her, but is shocked to discover that the body of his niece, whom he thought was a child, has now grown into that of an adult woman. Ruka's uncle grew up in a single-parent household for a long time without a wife or a woman, so when he sees Ruka naked, he can no longer suppress his sexual desire...