The story starts when a catholic schoolgirl Inaho discovers that a vampire, Mosquiton, who is believed to be an important and most powerful Vampire, is feeding off of her classmates. She stakes him, but he is revived after her blood comes in contact with his remains. Mosquiton becomes her slave and also a history teacher. Together, along with Yuuki and Honou, the unlikely duo have many escapades and adventures. One of Inaho's main goals is to find the mythical O-Part to make some more money (whatever it takes). . .