Yayoi (default name, can be changed) has lived in her aunt's house ever since her mother died. Her aunt is busy most of the time, so Yayoi spends her days alone. She discovered a collection of hentai manga left by her aunt's son, and got into the habit of reading it. Yayoi had soon become a perverted girl, masturbating nightly and yearning for a real sex partner.

One day her aunt introduces her to her new father, and Yayoi takes to him almost immediately, her lewd thoughts taking over. Her new father assaults her one night, but Yayoi takes it happily, and soon the two end up in an immoral, happily sexual relationship.