Nana, a high school girl attending a prestigious private school, is in a relationship with college student Yoshida. Since her father is busy with work and she lives almost independently, Yoshida—who once worked part-time at her house—started dating her. To Yoshida, Nana was not only a lover but also like a younger brother and even a father figure. They dreamed of a bright future together, enjoying their happy days. However, one day, a delinquent named Saji, who had been eyeing Nana, appeared and forced Yoshida into debt. This incident drastically changed their lives, leading them straight into the gates of hell.