Inaho, a Catholic schoolgirl, stumbles upon a vampire named Mosquiton preying on her peers. She defeats him with a stake, only to unintentionally revive him with her blood. Now bound to her as a servant and even taking on the role of a history instructor, Mosquiton joins forces with Inaho, Yuuki, and Honou. This odd quartet embarks on numerous thrilling escapades. Among Inaho's ambitions is the pursuit of the legendary O-Part, a quest fueled by the desire for wealth.