[[quoteright:300:http://tvtropes.org/pmwiki/pub/images/TVT-ChaosHead.png]]
[[caption-width-right:300:You only wish it was a harem show.]]

-->A shipping container on the roof. Sounds [[MindScrew crazy]], no?

''Chaos;Head'' is a VisualNovel starring Nishijou Takumi, a high school student and raging otaku.

Takumi lives in a steel shipping container on the roof of a building, converted into a small apartment. He spends most of his time at home, either playing the fictional MMORPG ''Empire Sweeper Online'' (in which he is Knight-Hart, the most famous and powerful player to exist) or watching anime. He has over one hundred "waifus" (figures), his favorite being the character Seira from the [[ShowWithinAShow fictional anime]] ''Blood Tune''; he frequently affirms his love of 2-D women and his hatred of 3-D women. He is a borderline {{hikikomori}}, having crafted a "minimum attendance shift chart" to ensure that he can attend school as little as possible while still graduating.

When the story begins, he is only know to have even semi-regular interactions with a few people: his bratty younger sister Nanami, his ESO guild partner Grim (whom he speaks to online), and Misumi, another classmate who his high school's resident playboy. Beyond these, he seems to be quite afraid of interacting with people, exhibiting classic signs of social phobia (such as extreme discomfort with making eye contact).

This routine life is shattered when, upon coming home one day, he hears the sound of something being pounded into concrete. Looking over, he sees a pink-haired girl pinning a body to an alley wall with cross-shaped stakes. The girl turns, smiles, and inexplicably calls him by name, at which point he runs. This scene is the third in a series of bizarre, gruesome murders called the "New Generation" murders.

The game has a unique "delusion trigger" system where the player can, at certain points, opt to view one of Takumi's daydreams/delusions. The player is given a choice between a good delusion (happy, humorous, or [[{{ecchi}} H]] in nature) or a bad delusion (paranoid, violent or tragic in nature). For example, when Nanami visits and berates Takumi for not ever calling home, she takes a swig of soda without asking; the good delusion brings up the concept of an IndirectKiss, prompting Takumi to compare it to a hentai game scene (at which point it almost does turn into one), and the bad delusion involves Nanami taking a swig of coke, then gagging and coughing up blood and dying. Takumi wonders why that happened, then remembers that he poisoned the coke beforehand. Typically these delusions have no direct influence on the story itself (Takumi simply snaps out of it and the scene continues from where it left off), but seeing certain ones triggers flags that can influence which ending you see. Many of these delusions involve blatant reference to anime (or eroge) tropes.

The game was made into an anime for the fall 2008 season, with an Xbox 360 updated rerelease titled ''Chaos;Head Noah'' released in February 2009.

A fan translation patch for the game was released in July, but was taken down from the main site due to an agreement with Nitroplus.
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Provides examples of:

* AGodAmI?
* ArcWords -- "Whose eyes are those eyes?" (''"Sono me, dare no me?"'')
* {{BFS}} -- The Di-Swords.
* BittersweetEnding
* BlandNameProduct: Deluoode for Google, and We-Key Pedophiria - seriously - for TheOtherWiki.
** The list goes on, believe me - Taboo! (Yahoo!), Slavecard (Mastercard), Grouchosoft Mindorz X Perfect (Microsoft Windows XP Premium... seriously), TWO different [=McDonald's=] spoofs ([=McDeinald's=] and [=WacTiKald's=])... there are easily a half dozen of these in each chapter of the game, and the anime adds in even more.
* BloodyMurder
* CallingYourAttacks -- Subverted; in the only instance, the character can't think of a name to use
* CannotStandThemCannotLiveWithoutThem -- Takumi's attitude towards "3-D" girls.
* CharacterBlog -- Part of the website for ''Chaos;Head Noah'' features blogs by each of the six main girls and one for Takumi.
* TheChessmaster -- [[spoiler: Norose]].
* CooldownHug
* CompleteMonster -- Norose.
* CreepyMonotone
* CrowningMomentOfAwesome -- [[spoiler: At the end of the AA/A routes, Takumi gets killed by the BigBad and after a series of questions concerning his identity and status as a delusionary being, starts regenerating no matter how many times he's killed until he finally destroys Noah II]]
* CuteMute -- Kozue, at first.
* DepartmentOfRedundancyDepartment -- [[spoiler:Serious-mode Yua]] has a habit of emphasizing sentences by repeating them several times in a row with slightly different phrasings.
* DiabolusExMachina -- Route B is one huge ever-expanding example of this, featuring among other things, [[spoiler:a DespairEventHorizon (Sena) and BodyHorror AndIMustScream (Kozue), all of which culminates in a LetThemDieHappy MercyKill JustBeforeTheEnd for a ShootTheShaggyDog ending]]. And the reason why it all happened? [[spoiler:Kozue got knocked unconscious during the earthquake]].
* DiagonalCut
* {{Dojikko}} -- Kozue. Also Yua, in the anime.
* DownerEnding
* EmotionEater -- This is how the Di-Swords function.
* {{Fanservice}} -- Some of the delusions Takumi is having qualify for this.
** The rest tend to be FanDisservice.
* FakeBand -- Phantasm. Their lead singer is FES, also known as Ayase Kishimoto.
* FirstNameBasis
* FlashForward -- The show starts with one
* FormulaicMagic -- fun[[superscript:10]] × int[[superscript:40]] = Ir2, [[spoiler:the equation Takumi discovered in elementary school and the basis of the Noah Project]]. What the equation actually signifies is never explained in depth.
* {{Geek}} -- Takumi
* GirlWithPsychoWeapon -- The entire core female cast.
* GoMadFromTheRevelation
* GovernmentConspiracy
* HairColors -- Fifty-fifty split - Rimi, Kozue and [[{{You Gotta Have Blue Hair}} Ayase]] have them, while Yua, Sena, and Nanami have more normal blonde and black shades.
* HandsomeLech -- Takumi's best(/only) friend Misumi.
* HarmfulToMinors -- Sena and her mother, sister and father. Wow.
* HealingFactor
* HeyItsThatVoice -- Kenta Miyake as Norose is basically reprising his role as Rosenberg in ElCazador, except with scary teeth and [[spoiler:a {{BFS}}]].
* HeyYou
* {{Hikikomori}}
* HotChickWithASword -- They all might use Di-Swords, but it's Sena who belongs to this trope.
* ImaginaryFriend -- Seira, from ''[[{{ShowWithinAShow}} Blood Tune]]''
* ThroughTheEyesOfMadness
* InterruptedSuicide -- [[spoiler:Ayase. Takumi's first conscious use of his delusionary abilities in the game is to create a flowerbed which breaks her fall after she attempts suicide by jumping off the roof of the school.]] And later on, [[spoiler:Takumi himself]].
* LaserGuidedAmnesia
* MindScrew -- With Takumi leading the narrative, not only does he not have any idea what's going on, the audience doesn't know much more than he does.
* TheMole -- [[spoiler: Suwa]].
* MoralEventHorizon -- Norose's treatment of Nana when [[spoiler:Rimi comes to rescue her]]. You can only really go downhill from there.
* MrImagination -- Takumi
* MultipleEndings
* MyNameIsInigoMontoya
* NewTransferStudent -- Kozue.
* NietzscheWannabe -- Norose.
* NightmareFuel -- Plenty of it - this is a Nitroplus game, after all.
**A sample: all the New Gen murders in the game have mysterious elements, particularly the second, in which the dead man has [[spoiler:an eight-month old fetus sewn into his stomach; given the age of the fetus, it had to have been removed from the mother's body before birth.]] It is eventually shown, in flashback, exactly [[spoiler:who the mother is]] and how this happened. This troper REALLY wishes it hadn't been.
* NinetyPercentOfYourBrain -- Norose's reasoning for how the abilities of Gigalomaniacs work. Also that 80% of the brain is used for processing visual data.
* {{Otaku}} -- Takumi
* PsychicLink -- [[spoiler:Kozue uses this to communicate telepathically. Kind of. It's stated that somehow it is entirely different because it runs off the power of delusions]].
* ScaryShinyGlasses -- Yua
* SlasherSmile
* ShowWithinAShow -- ''Blood Tune''. All the audience really knows about it is lead character Seira, who Takumi is deluded enough to see talking to him.
* SpoilerOpening -- The gradual reveal of the different Gigalomaniacs throughout the story isn't quite as exciting after you see all but two of them with their Di-Swords in the opening.
** The reveal of [[spoiler:Norose as the BigBad]] is also somewhat spoiled in the anime OP by the shot of [[spoiler:him grinning maniacally]].
** There's also the shot of [[spoiler:Hazuki and Suwa]] together... why would those two characters be even be associated? ...Oh...
* SuspiciouslyAproposMusic -- In all three versions of ''Chaos;Head'', the music by Phantasm is not only apropos, it's plot important, since it seems to be predicting the New-Gen events.
* TallDarkAndBishoujo -- Sena.
* TechnoBabble
* ThemeMusicPowerUp
* TomatoInTheMirror -- [[spoiler:Takumi is actually a delusion of...himself. The other him being what the protagonist him knows as "Shogun".]]
* TookALevelInBadass -- Takumi does by the end.
* TrademarkFavoriteFood -- Sena loves popsicles.
** There's also Momose and her pronounced fondness for Japanese sweets.
* TwelveEpisodeAnime
* UhOhEyes
* UltraSuperDeathGorefestChainsawer3000 -- ShowWithinAShow titled Blood Tune, and MMORPG titled Empire Sweeper.
* UpdatedRerelease -- ''Chaos;Head Noah'', for the [=XBox=] 360. Changes to the game include adding routes for each of the girls and changing it to widescreen.
* UnwantedHarem -- While [[spoiler:except for Rimi]] none of them are after Takumi romantically, elements of the genre are invoked in a fashion. Official art usually depicts Takumi with the six leading girls of the show in a way reminiscent of it as well.
** When Takumi [[spoiler:is being tortured in the final episode of the series]], he slips into a delusion of having a romantic comedy-like relationship with the girls.
* WellIntentionedExtremist -- Norose. The fact that he's also a NietzscheWannabe pursuing his goals to extremes that make him a CompleteMonster tend to make him less than sympathetic, though.
* TheWorfBarrage
* {{Yandere}}
* {{Yangire}} -- Two. Nice with some disturbing and murderous traits: [[spoiler:Kozue]]. Jerkass psychopath with a veneer of civility: [[spoiler:Suwa]].
* YouGottaHaveBlueHair -- Ayase.
* YourMindMakesItReal
* ZettaiRyouiki -- Rimi and Kozue.
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