As a Catholic schoolgirl, Inaho uncovers a shocking fact that her peers are under attack by a vampire called Mosquiton. Without delay, she puts a stake through him, but to her amazement, her blood revives him. Mosquiton pledges himself as her loyal servant and even takes on the responsibility of a history instructor. Together, Inaho, Mosquiton, Yuuki, and Honou embark on enthralling escapades and undertakings. In addition to this, Inaho aims to find the renowned O-Part to ensure a substantial sum of money.