Alucard von Mosquiton is a quarter-vampire bound by a blood contract to Inaho Hitomebore. He revives through human blood after being staked through the heart and reduced to ashes. This revival binds him to the blood's owner until he is staked again. Prior to Inaho, he served her great-grandmother under the same contract.

He possesses light purple hair, red eyes, and an ageless adult appearance. His primary weapon is a scythe. Alucard exhibits immunity to religious symbols like crosses and can drink blood without turning humans into vampires. He commands two elemental servants: Honoo (fire) and Yuki (ice).

His personal history includes centuries of separation from his vampire wife, Camille, and an ongoing rivalry with the vampire Earl St. Germain (also known as Count Sangermaine). Despite his blood-drinking nature, he claims a pacifist stance.

Functionally serving as Inaho's manservant and protector, he willingly obeys her commands despite finding her intimidating. He performs dangerous missions at her behest, often to ensure her safety during their quests. He harbors unrequited romantic feelings for Inaho, viewing his affection as one-sided.

His core role involves aiding Inaho's worldwide search for the mystical "O-Parts," artifacts rumored to grant immortality. This mission stems from Inaho reviving him using notes from her grandmother's grimoire, establishing him as her contracted supernatural ally.