Amazing Nurse Nanako [OVA]

In a mansion on a military base somewhere in Japan lives a mad scientist, two martial arts masters, an old witch (literally), and the woman who works tirelessly to feed them and keep the house clean. She’s also constantly thretened with being turned into the subject of one of the doctor’s experiments, and forced to train in feats of strenth and endurance. Meanwhile, behind the scenes, the doctor is watched over by powerful forces in the military and the Church, both with their own mysterious goals. Where does Nanako fit into this, and why is she the subject of so much attention? Who knows.