An moves to Tokyo to take her university entrance exams and stays with her brother and his wife. An is secretly perverted and has few friends of the same sex. Her sister-in-law, Hikaru, is friendly and talks about anything without hesitation. An gradually becomes attracted to Hikaru. While her brother is away on a business trip, Hikaru ignites An's erotic desires and tries to make her her sex slave. An gradually becomes drawn into a world of perversion.