Hone Onna began as Tsuyu, a human geisha skilled in crafting paper balloons. She loved Shinsaburo, who betrayed her by selling her to a brothel to settle his debts. Within the brothel, she forged a close bond with fellow prostitute Kiyo and met Tetsuya, a man who truly loved her. Prioritizing Kiyo's happiness, Tsuyu arranged for her escape with Tetsuya. On the escape night, however, Kiyo—overcome by jealousy—betrayed Tsuyu to the brothel owner, resulting in the murders of both Tsuyu and Tetsuya. Tsuyu's body was cast into a river, merging with the spirits of other betrayed women who shared her fate. This fusion birthed the yokai Hone Onna ("Bone Woman"). Transformed, Hone Onna wandered villages seeking human connection. Her inability to control her skeletal form caused others to flee. Ai Enma eventually found her and offered companionship. Sensing something within Ai, the hesitant Hone Onna agreed, becoming the third member of Ai's team and the only one among them with a fully human past. Hone Onna typically appears as an attractive woman with long black hair, often styled traditionally and secured with decorative clips, grey eyes, and frequent red lipstick. She favors traditional Japanese attire: usually a blue kimono with a dark blue border, a white nagajuban underneath, and a red obi tied unusually in the front, paired with white jika-tabi. Her appearance shifts across eras: one features a white kimono with floral patterns and a dark blue obi secured by a red obi-jime; another showcases a kimono with yellow and red borders, a magenta obi, and yellow obi-jime. During investigations, she adopts modern disguises like a light brown jacket with a gray top and black skirt, or a magenta jacket and skirt with high heels, styling her hair untied or in a ponytail. She uses the alias "Sone Anna" for human interaction. Generally mild-mannered, she expresses annoyance when called "old lady," a frequent taunt from Kikuri. She shows more empathy towards humans and their situations than Ai's other companions, occasionally displaying concern or sympathy. While valuing her relationships with Ai and the team, she harbors a consistent dislike for Kikuri. Beneath her composed exterior linger traces of human vulnerability regarding betrayal and abandonment. Her supernatural abilities include traveling between the human world and the Realm of Eternal Twilight, magically changing attire to blend into society, and manipulating memories to create illusions of familiarity. At Ai's request, she transforms into a red straw doll with a red string around its neck. Her most distinctive power is revealing her skeletal form—partially or fully—to intimidate targets, weaponizing it by penetrating human flesh with bone fingers. She is skilled in throwing knives, sometimes engulfing them in blue spirit fire, and exhibits contortionist abilities to access confined spaces, though extrication proves difficult. She also participates in investigating clients and targets for Ai's vengeance contracts. After Ai's temporary death, Hone Onna lived as a human bartender until Ai's spirit returned as a butterfly, prompting her to rejoin Ai's service. Later, she posed as a gym teacher at Yuzuki Mikage's school to observe student cases. When Yuzuki became interim Hell Girl, Hone Onna and Ren Ichimoku distanced themselves to investigate Tsugumi Shibata's sudden departure from Saigawara City, suspecting a link to Yuzuki's unresolved fate. Following Ai's return as Hell Girl, Hone Onna resumed her companion role. In one encounter, she intervened to save a pregnant woman from suicide, discovering the vengeful spirit of Kiyo—unsettled for centuries—possessed the woman. Hone Onna subdued Kiyo's spirit and later requested Ai guide Kiyo's soul to eventual peace.