[[caption-width-right:300:Warning -- Here, there be nightmares]]

-> "One of the others inside my head... awakens. Another and another and... who... ''who am I''...?"
-->-- '''Yosuke Kobayashi'''

A SerialKiller is loose in the streets of Tokyo, one that delights in leaving the gruesome remains of his victims on display for the police to find. Yosuke Kobayashi, a dedicated young cop with Japan's major crimes task force known as Investigations Section One, has been working diligently to solve these horrendous crimes that have captured the media's attention. Lately, though, his dreams have been haunted by blood, darkness, and worst of all, visions of himself standing above the dismembered victims with knife in hand.

Pushing these dark thoughts aside, Yosuke focuses all of his time and energy (and his brilliant knack for criminal profiling) into finding the monster behind these attacks and putting a stop to them once and for all. The killer makes it [[ItsPersonal personal]], however, when his next target turns out to be Detective Kobayashi's girlfriend, the [[StuffedInAFridge mutilated but still living body]] of whom the killer delivers directly to Yosuke's office. Enraged, Kobayashi finally manages to track down the psychopath who is responsible. When he finds the killer to be laughing and unrepentant, though, something within him ''[[GoMadFromTheRevelation breaks]]'', and the man who once was Yosuke Kobayashi becomes something irrevocably different.

Several years later, the man known as Yosuke Kobayashi is about to be released on parole, having served out his sentence for the crime of criminal negligence in the cold-blooded killing of the lunatic that maimed his girlfriend. Ever since the killing and his subsequent arrest, he has gone only by the name of Kazuhiko Amamiya. Amamiya claims that he is an alternate personality of Kobayashi (who is a victim of [[SplitPersonality Multiple Personality Disorder]]), and that the "Kobayashi" personality died when another, far more violent personality named Shinji Nishizono arose to take Kobayashi's revenge on the serial murderer.

Upon his release, Amamiya is recruited into a private criminal investigations firm: one that can make use of his [[TheProfiler unmatched profiling skills]], and that seems more than willing to overlook his disorder. Serial murders are on the rise, more frequent and gruesome than ever before. With the dark whispers of Shinji Nishizono echoing in his mind, Amamiya and his firm aid the police in their investigations. Though the nature and method of each new murderer is different, and there is seemingly no relation from one to the next, Amamiya soon finds a connection. Each of the killers has a strange mark on the white of their left eye, just beneath the eyelid. A mark in the shape of a barcode...

''[[DoomedProtagonist The same kind of mark that is on Amamiya's own left eye]]''...

''MPD Psycho'' is a PsychologicalHorror/[[DetectiveStory Detective]] {{Manga}} written by Eiji Otsuka (''[[KurosagiCorpseDeliveryService The Kurosagi Corpse Delivery Service]]'') and illustrated by Shou Tajima (''Film/KillBill'', ''VideoGame/{{Galerians}}''). It was originally released in 1997, and is currently being published in the manga magazine Monthly Young Ace. It is licensed in North America by Creator/DarkHorseComics. In 2002 the series received a six episode live-action miniseries adaptation, directed by controversial filmmaker TakashiMiike.

!!This series contains examples of:

* AuthorAppeal -- Eiji Otsuka has a thing for showing mutilated naked bodies of young women, massive body trauma from bullets and explosions, and EyeScream.
** And the [[BoundAndGagged BDSM]].
* BodySurf
* BrainFood -- Used in nightmarish fashion by one flower-loving serial killer who cuts open his victims skulls to use their brains as flower pots. ''While they're still alive''.
* BreakTheCutie -- The serial-killer in the first chapter taunts Detective Kobayashi by telling him that he raped his girlfriend, ''multiple'' times, while in the process of ''cutting off her arms and legs.''
* BrownNote -- The songs of Lucy Monostone has been shown to have mind-altering effects on its listeners.
* CharacterOverlap -- The cop Sasayama also appears in Ohtsuka's ''Manga/TheKurosagiCorpseDeliveryService'', plus a big scar on his head and minus a leg.
* DefectiveDetective
* DetectiveDrama
* {{Doppelganger}} -- [[spoiler: EVERYONE SEEMS TO HAVE ONE.]]
** This is later explained however [[spoiler: the same company responsible for the barcode killers also had an ''[[Film/TheIsland Island]]''-style side-business going on were they would clone the rich and famous in order for the clones to serve as spare parts.]]
* DudeLooksLikeALady -- It doesn't help that his name also happens to be ''Lucy,'' of all things.
** It is widely believed that Lucy Monostone was inspired by Marilyn Manson.
* EyeScream -- Brought into play frequently in the series, especially when a character decides to get rid of his own barcode once and for all.
* FateWorseThanDeath -- Many of the {{serial killer}}s in this series seems to specialize in inflicting fates worse than death on their victims. See BreakTheCutie and BrainFood for some specific examples.
* FingerInTheMail -- A killer sends one of the detectives looking for him the armless, legless torso of [[StuffedIntoTheFridge the detective's girlfriend in an ice chest]].
* {{Gorn}} -- Taken up to eleven in the live-action mini-series, as expected of director TakashiMiike
* GrandTheftMe
* HalfTheManHeUsedToBe -- Things didn't work out so well between [[spoiler:Kido]] and that subway train...
* MadArtist -- Lucy Monostone, a prolific musician who was killed in the 1960s, was also a known terrorist whose legacy spawned violent cults.
* MindScrew
* {{Pixellation}} -- The most gory scenes in the live-action series are pixellated. This is entirely averted in the {{manga}}.
* PsychicAssistedSuicide -- In a sorta kinda case of DemonicPossession, the personality of Lucy Monostone forces [[spoiler:Kimihiko]] to blow his own brains out.
* PsychologicalHorror -- The bread and butter of this series.
* RapeAsDrama
* {{Seinen}}
* SplitPersonality -- The driving force of the series are the myriad of personalities that share the body of Kazuhiko Amamiya, including a genius detective, a child, a cross-dresser, and a cold-blooded killer. And that's ''[[FromBadToWorse just getting us started]]''.
* StuffedInAFridge -- Detective Kobayashi's girlfriend, mutilated but still alive, is delivered to his office stuffed in an ice-chest... ''minus her arms and legs.''
* SuicidePact -- The mass suicide of [[spoiler:Lucy Monostone and his fanatical followers]] in the church.
* ThanatosGambit -- Lucy's [[spoiler:suicide]] seems to have been the kickstart the Gakuso project needed to get going.
* UnsoundEffect -- Both played straight and for humor often in the {{manga}} series. At one point, when the protagonist adjusts his glasses after a morale-boosting speech, his co-worker responds to the written sound effect with: ''"Did you just say 'Shining?'"''