Hone Onna is Ai's third companion, and she often takes the form of a sultry woman in a kimono with its obi tied in front. She dislikes being called "old lady". She becomes the red straw doll when necessary by tossing her red obi jime over her shoulder. Hone Onna and Ren investigate the people who make a contract and the ones they have a grudge against. She usually infiltrates human society in casual clothing to investigate cases, on these occasions she tends to use the pseudonym "Sone Anna". She has used throwing knives as weapons in the first season of the show, and has shown considerable skill with these weapons. Hone Onna also seems to have some skill as a contortionist, which allows her to squeeze into very small places. The name Hone Onna comes from the legendary creature of the same name, literally meaning "bone woman", which reflects her ability to expose the bones in her body to scare the victims of the revenge Ai delivers. It is revealed that she had been a geisha named Tsuyu who was betrayed by a man whom she had fallen in love with after he sold her to a brothel to be able to pay off his own debts. Tsuyu was betrayed again when she attempted to arrange the escape of a fellow geisha named Kiyo with a man who had come to truly love Tsuyu. Tsuyu and the man were later murdered by a Yakuza, and that same Yakuza cast Tsuyu into a river afterward. Spirits rising from human bones thrown into the river before merged with Tsuyu's restless spirit, transforming Tsuyu into the yōkai Hone Onna, in which form she later met Ai. Hone lives out her life as a human after Ai dies at the end of the second season. This proves to be short lived as Kikuri comes to recruit her several years later to become Ai's assistant again. After Yuzuki becomes Hell Girl, she and Ren investigate why Tsugumi is moving out of town. The two suspect it is because of Hajime and because Tsugumi was unable to save Yuzuki. Hone becomes Ai's assistant again when she replaces Yuzuki as Hell Girl.