Yoshikazu's father is at work, so he accompanies his mother on a hot spring trip with relatives. When he meets 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 desire, which her husband cannot satisfy. Rei awakens Yoshikazu to the joys of sex, and he approaches her again and again with the same crazy enthusiasm as a monkey. And Rei responds hungrily to his insatiable sexual desire...