Sakaido is a genius detective who can track down any criminal. But when his daughter is murdered, revenge lands him on the other side of the law. Now in prison, he helps the police solve mysteries using a system that invades a person’s identity. Little by little, a trail of blood forms, and it all leads back to his daughter’s murderer. (Source: Funimation)
The anime takes place in a world where investigators have the power to tap into a killer’s unconscious and see fragmented parts of their psyche. This is referred to as an “ID:Invaded”, a mental plane that can be digitally entered to collect clues regarding a killer’s victims, crime scenes, and even motives. As one traverses through an ID-Well, their sights and actions appear as digital projections in the real world for investigators to analyze in real-time. Since a person’s unconscious thoughts are rarely organized, everything within an ID-Well appears in a fractured or symbolic state, including the people and locations, and can only be temporarily put together by someone investigating the ID-Well. Additionally, ID-Wells can only be entered by victims or other killers. While it is possible to get hurt or die in an ID-Well, the Well traveler can simply be removed and re-injected into the Well again, though all previous memories from their time in there will be damage.
Field analysts assist ID-Well investigators using a tool called “Wakumusubi”, a sort of handheld radar gun that detects and collects delicate “cognition particles”, given off by a person’s intent to kill. The scanner can be programmed to collect the killing intent of a specific criminal, and add that information to their ID-Well. This helps flesh out the killer’s ID-Well for a more thorough investigation. Additionally, the memories of victims encountered in ID-Wells can also add important information to the environment.
The anime follows the investigations of Narihisago/Sakaido, a renowned detective now in prison, who is tasked with diving into the ID-Wells of various serial killers. Two years prior to the current events, Narihisago’s daughter Muku was brutally murdered by a serial killer. This prompted him to hunt down and murder the killer, earning him his prison sentence. He is still depressed and haunted by his daughter’s death, but also uses this as a motivation to take his work seriously and help save other serial killer victims. However, Narihisago’s ability to analyze a killer’s weakness has also led multiple serial killers to commit suicide during their time in prison, something the investigation team is wary of. Despite this however, it is shown that the majority of Narihisago’s colleagues have great respect for his work.
Rookie field analyst Hondomachi becomes an important side character during the anime after having a near-brush with death in the Perforator serial killer case.