A police detective known to his colleagues as Yousuke Kobayashi, an unassuming family man on the hunt for a serial killer who dismembers his victims. When the killer spots Yousuke on TV, he claims to see something familiar in the detective and retaliates by maiming Yousuke's girlfriend. Eventually, Yousuke tracks down the killer, at which point a new personality emerges: Shinji Nishizono, an arrogant and ruthless psychopath, who shoots the killer dead.
From this moment on, Yousuke's personality is supplanted by Kazuhiko Amamiya, a calm and serious criminologist who gets arrested and imprisoned for the murder of the serial killer. Throughout the story, Kazuhiko's personality shifts repeatedly, most often toggling between Kazuhiko Amamiya and Shinji Nishizono during the early chapters.
Readers can usually discern which personality is dominant at any given time, as Kazuhiko Amamiya is near-sighted and wears glasses, while Shinji Nishizono does not need them. After Shinji Nishizono transfers the personality of Kazuhiko Amamiya to Isono Miwa, he is killed by a member of the Gakuso Company.
