Atsuko Chūzenji, younger sister of onmyōji Akihiko Chūzenji, serves as a journalist documenting supernatural-linked dismemberment cases through investigative notes that supplement the main narrative. Her writings form a side story, exposing connections between the crimes, a research hospital, buried family secrets, and a cult orchestrated by a deceitful spiritual leader. Collaborating with news editor Morihiko Toriguchi and crime novelist Tatsumi Sekiguchi, she records discoveries of severed limbs encased in custom boxes, victim abductions, and the experiments of medical researcher Kōshirō Mimasaka, who fused machinery with human anatomy.

Her notes trace the influence of Shunkō Kubo, a fiction author whose stories eerily paralleled real-world events, and dissect the cult’s manipulation of perpetrators. Functioning as an analytical observer, Atsuko reconstructs timelines, disentangles human motives from supernatural beliefs, and clarifies ambiguities—such as Kanako Yuzuki’s familial ties and the financial motives driving her kidnapping. Her chronicle spans the case’s inception to its climax, detailing confrontations with Mimasaka and Kubo’s ultimate fate.

Positioned peripherally, Atsuko remains a dedicated chronicler, her documentation strictly confined to professional interactions and devoid of personal history. Her role crystallizes through meticulous observations, bridging gaps between evidence and enigma without straying beyond her purpose as an archivist of truth.