While his father is at work, Yoshikazu accompanies his mother on a hot spring trip with relatives. Upon meeting his aunt, Rei, for the first time in a long time, he is captivated by her unconscious closeness and voluptuous body... Rei, who also happens to catch a glimpse of his aunt's youthful, powerful cock, sets her sights on him, and uses him to release her daily sexual desires, which her husband cannot satisfy. Rei awakens Yoshikazu to the joys of sex, and he approaches her again and again with the same frenzied ape-like enthusiasm...