G-HISTORY presents a realistic reenactment of a high school girl's experience living with her aunt's family while attending school in Tokyo. Airi Fukuyama is a serious yet sexually curious teenager. However, her relatives—the crude aunt Fuyuko and her impotent husband Shigeharu Niyama—take an unusual interest in her. As the modest, proper girl is gradually exposed to the couple's blatant sex life, her suppressed desires begin to surface, intensifying day by day until she transforms into a lustful young woman.