La Blue Girl.

It began centuries ago, when the Miroku ninja clan made a deal with the forces of the underworld, leading to centuries of struggle between rival clans. And now, after more than 600 years of peace, the denizens of the underworld are about to get a new boss. Now, 16-year-old ninja in training Midou Miko is entrusted with the family business: making sure that sex-starved demons stay out of humanity's way! What does a ninja do? Fight, with every battle skill and sexual sorcery she can muster!