Yui is suffering from daily sexual frustration as her husband is constantly busy with work and rarely at home. One day, while masturbating in the bathroom, she is caught by her stepson Akira. Overcome with excitement, Akira touches Yui's body while she sleeps, but when she wakes up, he panics and tries to run away. Unable to resist the mix of pain and pleasure, Yui pulls him back and the two end up making love. From then on, Akira continually seeks out Yui's body. What began as an unexpected encounter forms a new, intimate bond between them.