Detective Minoru Sagisaka serves in Shinjuku’s Intervention Department, tackling cases steeped in supernatural phenomena. Three years before the central narrative, he and colleague Shouta Sawada witnessed inexplicable skyward disturbances over Shinjuku, compelling Sagisaka to join the Observation Department—a unit devoted to unraveling such enigmas. His resolve springs from personal tragedy: daughter Yoshiko survived a classmates’ massacre only to be institutionalized when officials dismissed her account of a supernatural killer. This fuels his relentless hunt for evidence to vindicate her testimony and restore their family’s honor.

Teaming with pragmatic detective Narumi Kure, Sagisaka probes a string of murders tied to mikuras—blood-drinking yōkai. Though Kure initially scoffs at supernatural explanations, Sagisaka’s fixation on occult forces reflects his crusade to validate his daughter’s sanity. Their partnership echoes investigative duos like Mulder and Scully, with Sagisaka assuming the believer’s mantle. His persistence fractures relationships with skeptical peers who deride his theories, yet he forges unyielding resolve against their scorn.

Resurgent mikura activity drives Sagisaka to link fresh atrocities to the three-year-old incident. His inquiry converges with survivors like Hinaru—a resilient rural migrant—and peaks during Eko’s citywide rampage. When the police chief morphs into the Ushi-oni yōkai and assaults sheltering civilians, Sagisaka throws himself before Yoshiko, absorbing the lethal blow. This final act cements his devotion to shielding Yoshiko and affirming their shared truth, paying the ultimate price.

Sagisaka’s journey shifts from a redemption-seeking investigator to a tragic hero whose sacrifices expose the mortal toll of supernatural warfare. His dual identity as father and detective intertwines with belief-versus-skepticism themes, grounding the narrative’s examination of hidden realms clashing with reality.