Kaya's mother is named Mirai Sato. She is a central figure in the story, as her background and actions are directly tied to the supernatural conflict that defines her daughter's life. Mirai appears to be an ordinary woman on the surface, but she is a member of the Ebisumori clan, a family with a long history of psychic abilities and dark rituals.

Her motivation is rooted in a deep, tragic trauma from her upbringing within the Ebisumori clan. Discovering that her family practiced rituals to birth evil spirits to destroy their enemies, she was driven mad by this knowledge. Her actions are driven by a desire for revenge against her own extended family and a desperate, twisted wish to end the curse that plagues their bloodline. At one point, consumed by grief and hopelessness, she believes the only way to stop the generations-long curse is to die and take her daughter, Kaya, with her.

In the story, Mirai is revealed to be pregnant with a powerful evil spirit that takes the form of her unborn child. This pregnancy is not accidental; she performed a special ritual to conceive Kaya with the intention of creating a curse that would destroy the Ebisumori clan. Her actions serve as the primary, underlying threat of the series, making her a tragic antagonist whose fury and pain drive the climax of the first season. Her choices directly impact her older sister, Nana, who tries to bond with Kaya, and are the reason the family is entangled with the paranormal reporter Mob and his psychic partner Namu.

Mirai’s key relationship is with her daughter, Kaya. The story explores the complicated nature of this bond, as Kaya’s own psychic abilities are a direct result of her mother’s ritual. Despite her mother’s actions, a pivotal moment occurs when Kaya shows her a drawing, which convinces Mirai to give birth to her second child and abandon her plan to curse the family. The series finale focuses on Kaya and her teacher, Chie, trying to stop Mirai, with a key moment involving Chie convincing Mirai that Kaya loves her and is not afraid of her. Mirai is also the younger sister of Nana and the daughter of Mutsu, the former head of the Ebisumori clan, who is eventually killed by the evil spirit Mirai is carrying.

A notable detail about Mirai is that despite being from a psychic clan, she does not appear to possess any inherent psychic powers of her own, which contributed to her status and treatment within the family. Her most significant development is in the finale, where she is seemingly brought back from the brink of her destructive plan through the compassion of her daughter and Chie, choosing life over annihilation.