The narrator is a man deeply affected by the disappearance of his teenage girlfriend. In his youth, he spends his time drawing maps of an imaginary town based on her descriptions. As an adult, he lives an isolated and lonely life, carrying the weight of his early heartbreak. He eventually takes a job as the director of a small-town library in the mountains, seeking a quiet existence while still holding out hope for a reunion with his lost love.

A neurodivergent teenager who spends his days reading in the local library rather than attending school. He absorbs massive amounts of information but struggles to find practical applications for it in his daily life. Often isolated from his peers and family, he finds comfort in repetitive routines and forms a fascination with the walled-in town.

The retired director and founder of the small-town library. A former sake brewery heir who used his personal wealth to establish the library, he takes a keen interest in the protagonist's life. He dresses distinctively, often wearing a skirt and a blue beret, and possesses a calm, empathetic demeanor shaped by profound personal tragedies involving his family.

A 16-year-old girl who struggles to differentiate between reality and her own dreams. She describes a walled-in town where her real self works in a library, claiming her physical body is merely a shadow. Her sudden withdrawal and subsequent disappearance leave a lasting impact on the protagonist.

A divorced woman who relocated to the small mountain town to open and run her own coffee shop. Like the protagonist, she lives a solitary life and relies on quiet daily rituals to find comfort. She forms a cautious connection with the protagonist, bonding over their shared experiences of loneliness and hesitation toward new romantic attachments.

An appendage separated from the protagonist in the walled-in town, reflecting his memories and physical form. Stripped of its connection to the protagonist, the shadow is forced to work on the outskirts of the town and slowly weakens without its human counterpart. It serves as a physical manifestation of the protagonist's ties to the outside world.

A dedicated and efficient librarian who essentially runs the daily operations of the facility. She is highly protective of the library and Mr. Koyasu's legacy. Careful with her words and guarded in her interactions, she provides the protagonist with necessary context about the town while keeping her own emotions private.

A strict enforcer of the rules within the walled-in town. He manages the town's perimeter, oversees the entry of newcomers, and performs difficult labor such as gathering and burning the remains of deceased beasts during the winter.

A former coworker of the protagonist from a book distribution company. He uses his professional connections to help the protagonist locate and secure a new position at a rural library.

A woman originally from Tokyo who commutes for years before settling in the mountain town. She shares a happy life with Mr. Koyasu until an unforeseen family tragedy shatters their existence, fundamentally changing the course of the library's history.

The young child of Mr. Koyasu, whose sudden loss deeply impacts his family and ultimately motivates his father to establish the library as a community space.

A resident of the walled-in town who cares for the protagonist when he falls ill. He passes the time by sharing a haunting story from his past about an inn and a ghost.

A local resident who struggles to understand his neurodivergent son. He visits the protagonist seeking answers about his child's disappearance, revealing the emotional distance within their family.

The older siblings of the savant teenager, one of whom is a medical student studying neurosurgery. They attempt to rationalize their younger brother's strange behavior and disappearance by analyzing his psychological state.