Tooru, striving to overcome his retake exams, suddenly finds himself receiving sexual training from his aunt Shiori. While washing her body in the bathroom, he gradually becomes aroused by touching her mature skin. In bed, he's teased by her masturbation before being led into full-fledged sex. Then, involving his friend Toshio, the trio indulges in a thrilling threesome, driving Shiori to writhing ecstasy. Absorbing the vitality of both men, Shiori is completely overwhelmed by their combined energy.