18 year-old Miko Mido, a ninja-in-training, is entrusted with the family business of making sure the Shikima, a clan of sex-starved demons, stay out of humanity's way. But when the rival Suzuka clan steals the signet case that symbolizes the demonic pact between the Miroku Clan and the underworld, Miko and her older sister, Miyu, become targets of the most dangerous race of perverts around!