Ken, a nephew preparing for entrance exams, is staying with his mother's sister Mako, who lives in Tokyo. However, Mako, who has big breasts, is always braless at home, and her large breasts and protruding nipples, which are clearly visible even through her loungewear, are so erotic that Ken can't concentrate on his studies at all. Just when Ken's patience is finally reaching its limit living with his aunt, who unconsciously plays erotic roles, Mako asks, "Hey, do you want to touch my breasts?" After learning that Ken is a virgin, Mako goes beyond her role as an aunt and begins to seduce Ken...