Marina and Airi's mother has left her husband, only to marry a younger man, Kouzou Akizuki. While Marina has accepted their new stepfather, Airi hates him for breaking their family. Furthermore, she soon finds out he is a sexual deviant, sniffing his underaged stepdaughters' underwear and secretly desiring to take their virginity. Their mother is often absent from home, allowing Kouzou to pursue his carnal pleasures to his heart's content.