Sei Michaela Gakuen Hyouriyuuki / School of St. Michael

In 1212, the despotic pope Innocent III sells orphans and loyal subjects from his church into slavery in order to rejuvenate and purify the holy walls. Angered by the church's betrayal, a faithful servant and leader of the orphans, Hans, throws himself into the sea and dies. Several centuries later, he is reborn as a young hermaphrodite nun, Aiko. She seduces all the nuns and takes over the local church, exacting revenge in the name of her principles and deep resentment.

#1 Sei Michaela Gakuen Hyouryuuki - OVA (2 episodes), light novel adaptation, 1990

#2 Sei Michaela Gakuen Hyouryuuki 2 - OVA (2 episodes), sequel, 1994