Kanako Yuzuki, a middle schooler introduced as Yoriko Kusumoto’s close friend, shares an intense bond rooted in their mutual conviction of being each other’s reincarnations. This belief fuels their nocturnal rituals of philosophical debates and moonlit dances, underscoring Kanako’s introspective intellect. Her detached poise and scholastic prowess cement her image as an enigmatic, revered figure among classmates.

Her existence fractures when Yoriko shoves her onto train tracks, inflicting critical injuries. Stabilized in a hospital, she is moved to a clandestine research facility led by Kōshirō Mimasaka, a physician connected to wartime human experimentation. During her confinement, Noritada Amemiya—her guardian harboring unrequited affection—arranges her kidnapping. She becomes the subject of a macabre procedure: Mimasaka preserves her head and partial torso via mechanical apparatuses encased in a box, sustaining her consciousness.

Kanako’s origins later unravel as the offspring of an incestuous union between her mother, Yōko Yuzuki (posing as her elder sister), and Mimasaka. This lineage, combined with her inheritance as her grandfather’s sole beneficiary, fuels blackmail by Mimasaka’s aide, Tarō Suzaki.

Her dismembered limbs emerge among a spate of grisly crimes tied to novelist Shunkō Kubo, who encounters her preserved head on a train. Obsessed with replicating Mimasaka’s methods, Kubo undergoes a horrific metamorphosis, paralleling Kanako’s state. Her condition acts as a psychological pivot: Yoriko spirals into guilt, Yōko commits murder to shield her, and Mimasaka’s atrocities are unmasked. The fallout sees Yōko arrested, the cult behind the crimes dissolved, and Mimasaka’s research exposed. Kanako endures, her mechanized consciousness a haunting emblem of postwar scientific hubris and existential dread.