Uketsu is a freelance feature writer living in Tokyo who specializes in macabre subjects and unusual stories. His reputation as an expert on strange phenomena prompts friends to seek his advice on unsettling discoveries. He approaches the floor plan mystery with a mix of skepticism and deep curiosity, recording and transcribing conversations to better understand the architectural anomalies. His investigative drive pushes him to look past surface details, though he remains wary of the dark implications of his findings.

Kurihara is a draftsman working for an architectural firm. He possesses a sharp eye for structural design and a highly active imagination, filling his small apartment with both architecture texts and mystery novels. When reviewing floor plans, he quickly moves beyond practical structural analysis to theorize about the human behaviors that would require such strange spatial arrangements. He approaches the investigation as an intellectual puzzle, often proposing dark, violent scenarios to explain the architectural dead spaces.

Yuzuki is an office worker in her mid-twenties living in Saitama Prefecture. She possesses a floor plan of a house with asymmetrical features similar to the one Uketsu is investigating. Growing up in a secretive household, she experienced an unusual childhood marked by the sudden disappearance of her sister. She seeks to reconnect with her estranged relatives and understand the dark history surrounding the properties associated with her family.

Shigeharu is the elderly head of a branch of the wealthy Katabuchi family. He lives on a large traditional estate bisected by a long hallway leading to a Buddhist altar, which he fastidiously maintains and cleans daily. Raised in comfort during Japan's postwar economic boom, he deeply fears losing his wealth and status. He enforces strict adherence to archaic family traditions, exerting controlling influence over the younger generations living under his roof.

Keita is Ayano's husband, having taken her family name upon their marriage. Studious and quiet during his school years, he formed a strong bond with Ayano after she showed him kindness when others targeted him. He is fiercely devoted to his wife and constructs elaborate, long-term plans to protect her from the oppressive traditions of her extended family. He actively orchestrates their living arrangements to maintain control over their environment.

Ayano is a mother and wife living in the unusual Tokyo house. As a teenager, she was abruptly removed from her immediate family to live with her traditional grandparents, exposing her to their strict and secretive lifestyle. She maintains a quiet demeanor, working part-time at a supermarket while attempting to build a safe environment for her child. She remains highly secretive about her past, even to those close to her.

Yanaoka is an expectant father looking for a home in a forested hillside area of Tokyo. He and his pregnant wife are charmed by the property but unsettled by an unexplained dead space between the kitchen and living room. Prioritizing his family's comfort and safety, he ultimately decides against the purchase when unsettling news surfaces about the neighborhood.

Yoshie lives alone in an apartment in Kumagaya City after divorcing her second husband. She married into the Katabuchi family and learned of their strict traditions from her father-in-law, Shigeharu. She made difficult choices during her daughters' childhoods that resulted in a fractured family, bearing the emotional weight of those decisions in isolation.

Kyoichi is a deceased man whose remains are discovered in Saitama Prefecture. The condition of his remains—specifically missing a left hand—draws attention to his case and provides a crucial forensic link to the strange houses being investigated by Uketsu and Kurihara.

Kiyotsugu is an intimidating man who serves as an enforcer and right-hand man for the elderly Shigeharu Katabuchi. Though he does not personally believe in the family's superstitions, he follows orders to secure his own financial benefits. He acts as a monitor, keeping watch over younger family members who relocate away from the main estate.

Misaki is the daughter-in-law of Shigeharu Katabuchi, living on the main family estate. After the sudden death of her husband from a heart attack, she is forced to raise her children under the strict, watchful eye of her father-in-law. She experiences severe confinement when the family learns about a physical difference in her second pregnancy.

Kimihiko is the eldest son of his family branch who elected to remain on the elderly parents' estate to look after them. His sudden death leaves his wife and children vulnerable to the controlling traditions of the household.

Yoichi is the eldest son of Misaki and Kimihiko. He lives in the tatami rooms of his grandparents' symmetrical house. His sudden death near the Buddhist altar is initially ruled an accident, though irregular details regarding the timeline and his fear of the altar suggest otherwise.

Momoya is a child born without a left hand, a condition that holds dark significance in the Katabuchi family's superstitions. He faces intense isolation and strict confinement under the family's historical traditions. Despite his traumatic upbringing, he displays a capacity for gentleness when introduced to a younger child.

Hiroto is the infant son of Ayano and Keita. His parents design their living spaces specifically to ensure his safety and separate him from the darker aspects of their household. He represents a new generation that his parents hope to raise free from the family's historical burdens.

Fumino is the wife of Shigeharu Katabuchi. She lives on the traditional estate and is familiar with the house's layout, occasionally patrolling the corridors at night when she hears unusual sounds.

Kaei is the historical patriarch of the Katabuchi family who built a highly successful business empire. When chronic illness forces him to step back, his controversial decision to pass leadership to his introverted eldest son over his highly competent but illegitimate younger son fractures the family for generations.

Soichiro is the introverted and less competent heir to Kaei's business empire. He struggles to manage the company after his father's death and watches his half-brother succeed where he fails. Desperate to explain his misfortunes, he becomes highly susceptible to superstitions and initiates a dark family ritual based on a shaman's advice.

Seikichi is the extroverted, natural leader of the historical Katabuchi siblings. Angered by his father's decision to pass the business to Soichiro, he leaves to establish his own highly successful enterprise. His success and frequent marriages create a sprawling rival branch of the family tree.

Ushio is a woman who escapes poverty through her arranged marriage to Soichiro Katabuchi. Her new life of wealth is overshadowed by her husband's distance and the subsequent collapse of his business. Terrified of returning to poverty, her mental health declines sharply, leading to a tragic incident that permanently alters the family's superstitions.

Chizuru is the unmarried sister of Soichiro Katabuchi. Her secret involvement with her brother creates a massive scandal that severely damages the family's reputation and business standing. She later gives birth to twin boys.

Momota is a child in the historical Katabuchi family who is born without a left hand. His father, Soichiro, views this condition as the result of a supernatural curse. He is placed in a sunless room and subjected to strict rituals devised to lift the perceived curse.

Asata is the twin brother of Momota. Following the advice of a shaman, his family designates him to act as a warden over his brother, enforcing the strict rules of their confinement.

Rankyo is a woman who convinces Soichiro Katabuchi that she has supernatural powers. She leverages his fears about his failing business and his wife's tragic death to institute a bizarre set of rituals involving his children, secretly aiming to alter the family's inheritance lines.

Shizuko is married to the wealthy Seikichi Katabuchi. Competing against his other wives to secure her own children's inheritance, she conspires with her sister to manipulate the rival branch of the family, financing the construction of an outhouse specifically designed for dark rituals.