Ванюдо

Assistant of Enma Ai, who becomes the black straw doll with a red string around its neck, the string probably originating as the red scarf he wears in human form. He also frequently takes the form of a burning wheel on Ai's coach when she goes to the human world to claim a soul. The coach incidentally bears the same black flame-crest that appears on the chest of those people who contract with the Hell Girl. At all other times, Wanyuudou appears as an older man whose eyes remain mostly shut, wearing a fisherman's hat and fairly old-fashioned Japanese clothing. Despite appearing quite mild-mannered at most times, Wanyuudou possesses considerable skills in martial arts.

Wanyuudou's name means "A wheel entering the road" a reference to the flaming wheel form he most commonly assumes. In episode 12 of Futakomori it is revealed that he is from the Samurai era and had been the driver for a princess' entourage, and failed to save them with all dying in the process. As a result, he became a yōkai terrorizing people in the form of a flaming wheel. It is Wanyuudou who first states he and his two colleagues owe Ai a grave debt because she saved them from falling into Hell. (Source: Wikipedia)