Hone Onna is one of the primary companions to the central character in her task of sending the wronged to hell. Her true form is that of a skeletal yokai, but she usually appears as a beautiful,妖艳 (yāoyàn) or alluring, woman. She is several hundred years old, though she is highly sensitive to any mention of her age, becoming annoyed when others refer to her as an old woman or an auntie. Before becoming a supernatural being, she was a human named Tsuyu. In life, she was taken in as a servant by the son of a pharmacy owner. This man professed his love for her but ultimately betrayed her by selling her to a brothel to settle his debts. While in the brothel, Tsuyu became close friends with another woman named Kiyo. She later tried to arrange an escape for Kiyo with a man named Tetsuya, who truly loved Tsuyu. However, Kiyo, driven by jealousy, betrayed the plan to the brothel owner. Tsuyu and Tetsuya were subsequently murdered by a man with a sword, and Tsuyu's body was discarded into a river. Her soul, filled with resentment, merged with the spirits of other wronged women who had met similar fates, transforming her into the vengeful spirit known as Hone Onna, or Bone Woman.

For a time after her transformation, she wandered near villages seeking human company, but she could not fully conceal her skeletal nature. People would flee in terror upon seeing her true form, which caused her great sorrow. Her existence changed when she was found by the series' central avenger, who offered her a place as a companion. Though initially hesitant, Hone Onna accepted, becoming the third and only one of the group to have originally been human. Loyalty is a core part of her personality; she is deeply devoted to her master and has stated she will eliminate anyone who interferes with her work. Her role in the story is primarily one of investigation and infiltration. She uses her alluring appearance and skills in disguise to gather information about both the clients who seek revenge and the targets of that revenge. During these undercover missions, she often adopts the alias Sone Anna, posing as a school gym teacher, a bartender, an office worker, or a nurse to blend into various environments. She is the most outwardly empathetic of the group, frequently expressing sympathy for the human suffering she witnesses, particularly for female victims of injustice.

In terms of relationships, she is fiercely loyal to her master and considers the other two primary companions, a one-eyed man and a rolling fiery head, as her precious comrades and friends. She shares a distinct relationship with a childish spirit who frequently calls her "old lady" or "auntie," which is a consistent source of annoyance for her. Her past experiences profoundly shape her motivations. Having been betrayed by a man who claimed to love her and by a woman she considered a friend, she values genuine loyalty and is quick to side with those who have been wronged. This is evident when she once asked her master to eventually save the soul of Kiyo, the friend who betrayed her, acknowledging their shared pain and tragic circumstances.

Throughout the narrative, she does not undergo radical personality shifts but demonstrates a committed consistency. After her master temporarily ceases to hold her position, Hone Onna lives as a bartender until being summoned back into service. In a later arc, when a different character temporarily takes on the role, Hone Onna and her ally refuse to assist the new master, instead investigating the motives of another former associate, showing her allegiance remains with her original master alone. As a yokai, Hone Onna possesses several notable abilities. Her primary power is the illusion of a beautiful woman, which conceals her true skeletal form. She can voluntarily reveal her bones, either partially or entirely, to intimidate others. She is skilled in throwing projectiles, often knives wreathed in blue spiritual flames that can burn the target on contact. When a contract is fulfilled, she can transform into a straw doll; her doll is distinctively dark red in color with a red string around its neck. Her other skills include magically changing her clothes, manipulating memories to create false familiarity with others, and traveling between the human world and the twilight realm where her master resides. She also displays some unusual physical abilities, such as contortion, though she sometimes has difficulty getting out of the tight spaces she can squeeze into.