Yuki acts as the familiar to the vampire Alucard von Mosquiton. She wields ice powers, but must transform from her youthful form into an adult to unleash her full abilities. Her appearance features blue-black hair, green eyes, and beauty marks beneath both eyes, with her heritage being a human/demon hybrid.

As a core member of Mosquiton's group, Yuki joins him and Inaho Hitomebore on their worldwide search for the mystical O-Parts. She works alongside Honoo, the fire elemental guardian, blending supernatural quests with maintaining a mundane school cover as part of their dynamic.