Mayoi Hachikuji is the ghost of an elementary school student who perished in a traffic accident on May 14th. Her death occurred as she desperately sought her mother's home after her parents' bitter divorce severed their contact. This profound regret over failing to reach her destination transformed her into the "Lost Cow," an aberration causing individuals subconsciously avoiding home to become perpetually lost. Her presence disrupts navigation systems and prevents followers from arriving anywhere, though paths created after her manifestation offer an escape. After resolving her regret, she consciously suppresses this power. She retains the appearance of an 11-year-old girl: long black hair styled in pigtails resembling snail antennae, dark red eyes, and a white headband. Her constant attire mimics a school uniform: a white blouse with straps connected to a dark blue skirt, white socks, and pink shoes. A large pink backpack shaped like a chick or bird, overflowing with plush toys, defines her silhouette, evoking her symbolic snail motif. This backpack remains integral even when its contents change. In specific alternate realities or circumstances, she manifests as a 21-year-old woman—first as a pragmatic, combat-geared survivor in a post-apocalyptic wasteland, and later as a shrine maiden following her ascension to divinity. Outwardly cheerful, energetic, and childishly inquisitive, she playfully misspells words and deliberately mispronounces Koyomi Araragi's surname as a recurring joke, often excusing it with "Sorry, I bit my tongue." Her initial brattiness and coldness towards strangers mask a protective instinct, aiming to deter others from her aberration's effects. Beneath this youthful facade lies significant maturity, particularly evident when she offers guidance to Araragi on supernatural or personal matters. Their deep friendship thrives on banter and frequent, mutually enjoyed playful physical altercations. Her story begins when Araragi encounters her while avoiding home. With occult expert Meme Oshino's help, he locates her mother's former address, now a vacant lot, resolving her regret and transitioning her from an earthbound spirit to a wandering one free to visit Araragi. She later assists in finding the vampire Shinobu Oshino and advises Araragi on hiding his vampiric nature. A pivotal event occurs when Araragi and Shinobu travel back to prevent her death. While successful in that timeline, ensuring she reaches her mother alive, their return reveals catastrophic consequences: Araragi's absence leads to his death and a zombie apocalypse. In this reality, the adult Mayoi survives as a fighter trained by Oshino, rescues the time travelers, and delivers crucial instructions before the original timeline is restored. Confronted with this outcome, she later tells Araragi that while her death was tragic, she treasures meeting him as a ghost. Her existence as a spirit attracts the malevolent Darkness. To protect others, she sacrifices herself to this entity but is later revived alongside Araragi through supernatural means. Ultimately, she ascends to become the goddess of the North Shirahebi Shrine, presiding over Naoetsu Town and ending her eternal wandering. This divine role eradicates her prior timidness, enabling calm interactions with powerful beings like the vampire Kiss-Shot Acerola-Orion Heart-Under-Blade. Her name reflects her nature: "Mayoi" means "lost" or "to lose one's way," while "Hachikuji" combines the characters for "eight," "nine," and "temple," signifying an 89th temple—a reference to Buddhist pilgrimages involving 88 temples, with the 89th representing misfortune. The numerals 8 and 9 also read as "yaku," meaning misfortune, symbolizing her origins as a lost spirit associated with wandering and ill fate.