Lee is a university student who has taken a semester off from New York University to hide in Japan. He heavily uses sedatives like Ativan to suppress the memory of allegedly murdering his roommate, though his mind is full of sensory gaps and blank spots. Deeply protective of his father's health, Lee tries to maintain a calm facade while investigating the architectural impossibilities and temporal anomalies of his new home.

Sen is a teenage samurai-in-training living in 1877. She undergoes brutal traditionalist regimens to earn the approval of her demanding father following a failed samurai rebellion. Dedicated and fierce, she struggles with the cognitive dissonance between the honorable warrior ideals she idolizes and the harsh reality of her family's isolated, impoverished existence.

James, known as Jim to his son, has recently relocated to an old samurai house in Chiran. He reportedly suffers from a stress-related heart condition, prompting Lee to carefully manage his environment. Outwardly a normal parent, James exhibits subtle tensions, lies about small details, and keeps a locked study that heightens the mysteries of the household.

Itaro is Sen's strict father and the sole survivor of the failed Satsuma samurai revolt. Having retreated into hiding with his family, he imposes a brutal code of austerity and martial discipline on his household. He frequently tests Sen's loyalty and warrior spirit, using harsh methods to forge her into a weapon.

These figures occupy distinct roles across the timelines of the Chiran property. In the present, Hina is James's compassionate girlfriend, offering Lee kindness and local ghost stories. In 1877, Youna is a gentle maid serving the Iwasaki family. Otohime is the legendary sea goddess from the Urashima Tarō folktale, whose oceanic myth deeply influences the atmosphere of the coastal setting.

Lee's mother vanished from a hotel in Cambodia when Lee was twelve years old, leaving behind only suitcase tracks in the sand. Her disappearance deeply traumatized Lee, leaving him with a fear of open doors and an obsession with enclosed spaces.

Sen's mother lives in hiding with the rest of the Iwasaki family. She struggles with the severe poverty and harsh conditions imposed by her husband. She frequently clashes with Itaro over the lack of food and is critical of Sen's unwomanly warrior training.

Seijiro is Sen's younger brother. Unlike Sen, he resents their family's poverty and the strict martial expectations placed upon them. He frequently mocks Sen's dedication to her warrior training and lacks her intense discipline.

Kotaro is the youngest sibling in the Iwasaki family. As a baby, he is largely shielded from the immediate physical training his older siblings undergo, though he remains vulnerable to the harsh environment his father dictates.

Kura is Sen's deceased younger sister. She died during a past famine when Itaro withheld food from her as part of a brutal plan to build discipline. Her memory haunts Sen, particularly during moments of deprivation or fear.

James Baldridge is Lee's university roommate at New York University. Lee arrives in Japan convinced he has killed James, though his memories of the motive and the disposal of the body are completely blank.

Kono Sensei is Sen's childhood martial arts instructor. He suggests sparring as an alternative to Itaro's brutal methods, showing a slightly more humane approach to samurai training than Sen's father.

Fujita Torazo is a childhood bully who spars with Sen during her early training. When he gains the upper hand, Itaro escalates the conflict by giving Torazo a real katana, leading to a tragic outcome.

Maeda is the only remaining ally of the Iwasaki family. His sudden disappearance plunges Itaro into paranoia, as the family fears Maeda may have revealed their location to the imperial government.

Okiku is a servant girl from local folklore who was murdered by a cruel samurai and thrown down a well. Her story serves as a grim local legend that sets the atmospheric tone for the house's dark history.