Mayoi Hachikuji is the ghost of an 11-year-old girl who perished in a traffic accident on May 14th, the day before Mother's Day. Her death occurred while she was running away from her father's custody in a desperate attempt to reach her mother's home. The bitter divorce of her parents had severed contact with her mother, causing Mayoi to gradually forget her mother's face. This unresolved longing to reconnect bound her to the earth as a "Lost Cow" aberration, an existence that causes those encountering her to lose their way. She appears with long dark hair in pigtails, a white headband, and a school uniform: a white blouse with straps connected to a dark blue skirt, white socks, pink shoes, and a distinctively large pink backpack resembling a bird or snail shell. Her personality seems outwardly cheerful and energetic, characterized by deliberate spelling errors and mispronouncing names, especially Koyomi Araragi's surname. Initially mistrustful of strangers, she actively pushes people away through hostile behavior to shield them from her aberration's effect. This defensive rudeness masks an empathetic nature, as she seeks to avoid imposing her lost condition on others. Despite her childish demeanor, she displays maturity when offering guidance or listening to problems. As a Lost Cow aberration, Mayoi passively causes navigation systems to fail and individuals following her to become disoriented, preventing them from reaching destinations—a manifestation of her unresolved regret. Her ghostly nature grants immortality, agelessness, and the ability to instantly restore damaged clothing. She requires no sustenance but can consume food voluntarily. After resolving her core regret, she suppresses these abilities to avoid harming others. In her initial encounter, Araragi helps her locate her mother's former residence, now a vacant lot. Acknowledging this site as her destination allows her transition from an earthbound to a wandering spirit. She subsequently reappears periodically, maintaining her friendship with Araragi and advising him on supernatural matters, including whether to reveal his vampirism to his family. During a time travel incident, Araragi and Shinobu Oshino accidentally prevent her childhood death. This alteration creates an apocalyptic timeline overrun by zombies, where an adult Mayoi survives as a 21-year-old warrior trained by Meme Oshino. In this reality, she rescues the time travelers and delivers critical information before they restore the original timeline, where her death remains inevitable. Mayoi later expresses gratitude for meeting Araragi as a spirit, acknowledging her death enabled their meaningful connection. When pursued by the entity "Darkness," she willingly sacrifices herself to protect others. Following temporary resurrection during Araragi's own revival, she becomes the goddess of the North Shirahebi Shrine, ending her wandering existence. As a deity, she oversees Naoetsu Town, monitors supernatural activity, and establishes protective barriers that retain her disorienting effects. Her name "Mayoi" (真宵) means "true evening" but is homophonous with "迷い" (lost). "Hachikuji" (八九寺) translates to "89 temples," referencing Buddhist pilgrimage traditions where the 89th temple signifies misfortune ("yaku") for exceeding the standard 88. This etymology reflects her tragic fate and supernatural role.