Nana, who lives with her father who is often away on business, spends her days almost as if she is living alone. Nana was a quiet and good-student schoolgirl, but she has a tendency to fantasize, and imagines having sex with older men and indulges in masturbation. One day, she is attacked in her sleep by Masakazu, a man from the neighborhood who brought her a notice, and they have sex. This leads to her being noticed by Masakazu's brother Taro, a gangster, and Taro's boss, Hirai, a delinquent middle-aged man, and she falls into a life of debauchery...