[[quoteright:262:http://static.tvtropes.org/pmwiki/pub/images/majin-tantei-nougami-neuro-episodes-online_4298.jpg]]

->''"This mystery is already on the tip of my tongue..."''

Majin Tantei Nougami Neuro (“Demon Detective Neuro Nougami” but popularly [[{{Woolseyism}} Woolsey’d]] into “Private Evil Eye Neuro Nougami”) is a supernatural detective manga and later anime that follows Neuro, a [[ExactlyWhatItSaysOnTheTin demon]] who literally ''eats'' mysteries. Having eaten all of the mysteries in Hell he goes to Earth in search of the ultimate mystery. There he meets Yako Katsuragi, a schoolgirl whose father was recently murdered. In order to keep his identity as a demon secret Neuro sets up a detective agency under Yako’s name, pretending that she is a brilliant schoolgirl detective and he her assistant. With the aid of his [[SwissArmyWeapon 777 Tools of Hell]] Neuro spends his time solving the murders he deems interesting while, naturally, [[KidSidekick dragging Yako along with him]].

The plot itself bounces between solving the individual cases of [[MonsterOfTheWeek one time]] murders and much larger overreaching situations such as the mystery of the Phantom Thief X. Perhaps the most distinctive feature of the series is when the culprit reveals his/her true nature and transforms into another form entirely. At this point Neuro reverts to his [[GameFace demon form]] and devours the mystery. That said, it should be noted that since any bystanders (Yako excluded) never see Neuro doing this it can be interpreted as more of a mental representation.

While the search for the [[MacGuffin ultimate mystery]] at seems like a typical ExcusePlot for a MysteryOfTheWeek setup, once the character dynamics and the world are established, [[GrowingTheBeard the series kicks into high gear]] with the [[ItWasHisSled HAL arc]]. As it turns out, despite the usual {{Shonen}} conventions, Neuro was [[CassandraTruth not kidding]] when he said that he was starving to death. A main character that is [[CrutchCharacter gradually growing weaker]] the more he [[HeroicRROD uses his power]] instead of getting stronger becoming more absurdly strong than he was before, a female character whose [[CharacterDevelopment growth]] is [[TookALevelInBadass important to the story]] and a [[CrazyAwesome whole]] [[HumansAreInsane lot]] [[AlwaysChaoticEvil of]] [[LoveMakesYouCrazy crazy]] [[IllGirl people]] make this a very unique and surprising series.

Both the manga and the anime are complete at 202 chapters and 25 episodes. GeckoEnding beware.

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!!This series features examples of:

* [[AbuseIsOkayWhenItIsFemaleOnMale Abuse Is Okay When It Is Netherworld Detective On Unlucky Schoolgirl]]: And any person who has the misfortune to meet Neuro. Just ask Godai.
* AlternateCharacterReading: Common in the anime's episode titles.
* AmbiguouslyGay[=/=]MistakenForGay: Godai. Maybe. On one hand, Neuro seems to think so, complete with literally throwing musclemen magazines at him. On the other hand, Neuro would do that sort of thing anyway because that's how he [[{{Troll}} rolls]]. On yet another hand, Godai denies it. On the final hand, Godai's encounter with a CampGay policeman indicated that his life apparently works like a gay DatingSim. So it all comes down to a big who knows.
* AmusingInjuries: Unlike many examples, the series has no qualms with subjecting female characters to this. [[ButtMonkey Poor Yako.]]
* [[spoiler: AndTheAdventureContinues]]
* AnimalMotif: Quite a few villains have one. Especially obvious with the [[spoiler: creator of the social network (bees) and the bomber mom (dogs).]]
** Neuro himself is a toucan-parrot thing.
* AntiHero: Neuro is a very strong NominalHero if not outright VillainProtagonist, while Sasazuka is an AntiHero [[spoiler: after his arguable FaceHeelTurn]]
* AntiVillain: [[spoiler: Professor Harukawa / HAL. He just wants to [[{{Necromantic}} bring back his true love]].]]
* AnyoneCanDie: Sicks has killed off and corrupted major characters that we didn't expect him to. The most notable being [[spoiler: Sasazuka and Sai.]]
* AppliedPhlebotinum: Neuro's 777 "hell techniques". (Perhaps it should be 666, but as long as you view a daemon as a fallen angel, 777 fits well)
* AsLongAsThereIsEvil: Neuro has a plentiful supply of "mystery-SerialKiller energy" because we as humanity are [[AlwaysChaoticEvil genetically disposed to its hidden evil nature]], and that [[spoiler: [[BittersweetEnding eventually someone just as evil as Sicks will emerge onto the scene]].]]
* AuthorityEqualsAsskicking: Early in the manga, there's a throwaway exchange where Neuro is talking about how in his world, it's normal for the weak to submit to the strong. The person he's talking to asks if there's anyone Neuro would submit to. The answer is no. The obvious conclusion was later confirmed. Another clue was the long version of the name of the Seven Weapons [[spoiler: of the Demon Emperor]].
** Sicks to the New Bloodline
* AwardBaitSong: [[http://www.youtube.com/watch?v=PZSxignamsM Kodoku no Hikari]] the ending song of the anime.
* BackToBackBadasses: Anime only. Sasazuka and Godai have one towards the end. While Godai has his [[WithMyHandsTied hands tied behind his back]] no less!
* BadAss: Neuro, so very much, but he's not alone, Sai, Sicks and the New Bloodline also count.
* BadassNormal: Detective Sasazuka.
*** Though it's put into question when he states that he's lived two weeks on nothing but beer, sunlight, and salt, and acting like [[spoiler: coughing up blood]] is nothing to be jumpy about. He even encourages Yako to [[spoiler: visit him in the hospital after having just coughed up blood.]]
** Naohiro Usui, during the Sicks arc. He boosts up his game and attempts to stop Sicks, even outmaneuvering one of Sicks' top men and leading them into a trap.
** By the late manga, Yako. [[SoProudOfYou According to Neuro]], if a normal human is equivalent to a paramecium, then at one point Yako's a pillbug. A complex, multicellular lifeform with built-in armor, thousands of times a paramecium's size.
* BadassPacifist: Yako. Using nothing more then her empathetic abilities and sincerity to defeat those even Neuro could not.
* BeneathTheMask: The series frequently explores this concept, with every villain having this in some way: until the criminal is revealed, everyone acts normal. The moment it is revealed, they shed their masks and usually become sadistic and cruel. However, it's also used for the heroes, usually to show more caring natures.
** [[spoiler:...But then you have Sasazuka. Normally cool and level-headed, he is a force to be feared. It's not just that he can superior aiming skills, he will '''''kill''''' you if you don't tell him what he wants when he's serious about it. In particular, Godai tells a story about how Sasazuka once went to a big-named thug for information: Sasazuka was ruffed up, then within minutes the thug was being held off a 25-story building with twice the amount of injuries Sasazuka was shown being given. And, during this little story, Sasazuka is busy killing Sicks men with a PsychoticSmirk.]]
* BigEater: Yako never gets full, paralleling Neuro's appetite for mysteries.
** This is increasingly {{Flanderized}} as the series continues to the point that she regularly eats meals several times her mass and has admitted to trying to eat underwater before. One scientist even comments that what she does is physically impossible.
** That said, even she will run from her mother's cooking. One, and this term is used loosely, "concoction" is radioactive and safe to approach in fifty years or so.
* BigNo: See CoolAndUnusualPunishment below.
* BittersweetEnding: [[spoiler: The BigBad is dead, but Neuro has to return to the netherworld since he's nearly on his death bed, a large percentage of the Japanese population has been killed during the terrorist acts of the New Bloodline and several important characters like Sasazuka, Sai and Fumio have died due to their connections to the BigBad. And TheDragon survived his would be death [[DragonAscendant and has taken over as the pinnacle of evil]], and there's no permanent solution to prevent more people like Sicks from showing up since we're all inherently insane. But life goes on and Yako becomes a negotiator and Neuro returns eventually.]]
* BlackAndGreyMorality: Neuro doesn't solve mysteries out of altruism, [[BlueAndOrangeMorality merely to eat the evil intent of murders]], he comes across as good merely because the enemy happens to interfere with his meals. His opponents on the other hand, range from [[SlidingScaleOfAntagonistVileness petty to absolutely monstrous]].
* BlueAndOrangeMorality: Neuro, to the point of {{Xenofiction}}. At first, it seems as though he's forcing Yako into this, has no respect for her & views her as an inferior life form equivalent to a paramecium. Then, the series shows how Neuro acts towards people he detests (Sai), [[TranquilFury considers far over]] the MoralEventHorizon [[spoiler:(Sicks)]] and actually holds in contempt [[spoiler:(Yako, when she decides to stop being a detective)]]. Realizing that Neuro treats Yako that way because he actually respects her and is often proud of her verges on MindScrew.
* BrainsAndBondage: Neuro and Yako, anyway. [[spoiler:The [[BondageIsBad New Bloodline]], not so much.]]
* BrokenAesop: Ep. 14 ends with a message about how people shouldn't be so intolerant of other people's cultures. The irony is that this is delivered in reaction to the antics of possibly the most xenophobic and offensive depiction of an American in anime since 1945. Of course, a later chapter reveals that the American was [[spoiler:the first test subject of the electronic drug,]] so the {{Aesop}} is strongly reinforced, since if Yako and the others hadn't been blinded by stereotypes of Americans, they would have noticed something wasn't right much earlier. So, [[SpaceWhaleAesop don't be blinded by xenophobia or]] a [[AIIsACrapshoot crazy computer]] will conquer the world?
* ButtMonkey: Ishigaki. To a lesser extent, Yako and Godai for Neuro.
* CardCarryingVillain: One of the most disturbing examples ever; the series explores what would happen if someone really ''believed'' in being Evil. [[spoiler: Something, the New Bloodline, especially their leader Sicks, embody this principle.]]
* CastFromHitPoints: Neuro.
* CatchPhrase: "The mystery is already on the tip of my tongue."
** "The criminal is... ''you!''"
** "Itadakimasu/Let's eat!" in the anime.
* CharacterDevelopment: Unusually for a {{Shonen}} manga, Yako's is a major focus, with Neuro undergoing some as well.
* ChekhovsGun: Several. For example, Neuro mentions a few details about himself either right out or offhand that turn out to be very important. The fact that he's starving to death and needs mysteries to feed on seems like an ExcusePlot that [[WrongGenreSavvy certainly wouldn't be a real problem]] for an invicible {{Shonen}} hero until the HAL arc, where Neuro gets exhausted and seriously hurt for the first time. [[spoiler:And there's no miraculous cure or power up.]]
** Another is the murder of Sasazuka's family and the connection to Sai; [[spoiler: it both leads the protagonists and Sasazuka down to finding Sai and gives Sai his inspiration for a modus operandi.]]
* CluelessMystery: A big user of this trope.
* {{Consulting A Convicted Killer}}: Aya Asia often advises Yako.
* ContinuityCameo: The anime has cameos of a few characters that are in the manga but are not otherwise used in the show.
* CoolAndUnusualPunishment: At the end of HAL arc, Higuchi is forced to [[spoiler: watch 12 hours worth of etiquette training CD]].
** And then it happened again but this time with [[spoiler: 24 hours of tapes.]]
* TheCoronerDothProtestTooMuch: Yako's father was killed via his head being cut off with a chainsaw, and his blood was used to paint the walls. Since there was no way to enter the room, it was ruled a suicide by the police.
** Only in the anime. In the manga, his body was pincushioned with knives. And in the manga the police don't think it's suicide, obviously.
* CrazyCulturalComparison: Neuro makes a few comments on how human society is different from his own.
* {{Crossover}}: In one of the omakes of ''{{Muhyo And Roji}}''.
* {{Deconstruction}}: Of the concept that villains are always GoodAllAlong and/or have a FreudianExcuse for their actions, especially in the New Bloodline arc.
* DecoyProtagonist: Arguably, Neuro. The series spends a lot of time on Yako's character growth.
* DemotedToExtra: In the manga Ai is Sai's loyal partner in crime and {{Foil}}. In the anime she only appears once as a cameo.
* TheDeterminator: Detective Sasazuko spends over 10 years searching for the perpetrator who killed his family. Averted with [[spoiler: X (Sai)]], who kills people in order to search for his identity.
* DissonantSerenity: [[spoiler: Sai is more or less the very incarnation of this trope.]]
* DrivenToSuicide: [[spoiler: Honjou towards the end. And long before that Higuchi's parents.]]
* {{Eagleland}}: Again, episode 14, which takes this trope farther than any show before it, which is [[RefugeInAudacity very far indeed]]. However, it turns out that [[spoiler:Professor Harukawa chose him as the first victim/test subject of the electronic virus. Harukawa]] using the American as the trial run, since people would believe an American would do something like this, makes this an {{Exploited}} trope.
* EverythingIsOnline: The classic "hacker controls the traffic lights" variant.
* EvilChef: Shirota.
* EvilDiva / MusicalAssassin: Aya Asia. She can blow your brain with her song. Don't worry, [[BlatantLies I'm just kidding]], though she's not as malevolent as most examples
* EvilGloating: What Neuro does every time he beats an enemy -- often accompanied by ironic torture.
* EvilMentor: Neuro to Yako, also Aya Asia to Yako. And those two mafia guys... Yako has a lot of these.
* EvilVersusEvil: Neuro vs. all of the villains, with Sicks being the most extreme
* EvilVersusOblivion: Neuro vs. Sicks, one wants humanity to survive so he can continue to feed off of their evil intent as well as [[{{Troll}} mess with them]], Sicks just wants humanity extinct for his New Bloodline
* EvolutionaryLevels: Neuro uses this to describe the times Yako TookALevelInBadass. Learning to read people, developing super strength, and so on. Being Neuro, he still manages to make this sound insulting, but if later-series Yako is to a normal human what a complex, multicellular organism with built-in armor is to a paramecium?
** Also the criminals, early ones had a GameFace once their TrueColors were shown, but by the end of the series, the New Bloodline had developed their evil intent enough to manifest as a BattleAura.
* FaceHeelTurn: [[spoiler: Sasazuka in the latest chapters partially performs one of these, changing from a hero to a not-quite-villainous, but significantly more ruthless VillainProtagonist , in order to seek revenge against Sicks for the murder of his family. He doesn't get to enjoy it for long, though, as the confrontation ends in his FamilyUnfriendlyDeath ]]
* FateWorseThanDeath: What awaits you the moment you ''really'' piss off Neuro.
** Sicks too if he doesn't kill you outright.
* FauxAffablyEvil: Tierra is the most prominent example.
* {{Fetish}}: The page image [[http://static.tvtropes.org/pmwiki/pub/images/neurota8.jpg linked here if it's been changed.]]
** Neuro himself might count, although possibly not on purpose. Then again, it's hard to handwave all that [[OralFixation random object licking.]] Among other things.
* FourEyesZeroSoul: Naohiro Usui at first. He gets a [[CharacterDevelopment good]] [[JerkassFacade deal]] better as the series goes on.
** Averted with Higuchi, though he doesn't always wear his glasses and instead keeps them up on his forehead most of the time.
* GeckoEnding: Instead of introducing the New Bloodline, the anime has a confrontation with Sai in ''Brazil.'' She meets a bunch of {{Yakuza}} Aztecs: a random touch of {{Mayincatec}}.
* GenreShift: Somehow we started with a detective anime, led into the computer-focused HAL arc, and then... Yakazuka Mayans? [[WhatDoYouMeanItWasntMadeOnDrugs What?]]
** In the manga, instead of that last part, it turns into an action series with Neuro facing against a group called The New Bloodline. However, the series manages to go about it in a completely different way than most other action anime and manga, with, among other things, Neuro actually growing weaker as the series goes on, and the regular humans even managing to take out two of them by themselves.
* GivingSomeoneThePointerFinger: Yako, under Neuro's influence, OnceAnEpisode: "Hannin wa... ''omae da!''" or "You are... the killer!"
** Ishigaki tried it once in the anime. Needless to say he failed.
* GoneHorriblyRight: HAL [[spoiler:was stuck doing exactly what he was made to do, knowing that it was impossible and he'd kill a lot of innocent people in the process.]]
* GoOutWithASmile: [[spoiler:Sasazuka.]]
* GrievousHarmWithABody: Sometimes Neuro likes to use Yako as a club.
* HotSpringsEpisode: And poor Yako does not even get to enjoy the hot springs because one of Neuro's devilish creatures was set loose on the water.
* HumanityIsInfectious: Averted, or so Neuro claims. Since he's fundamentally incapable of understanding how the human mind works, that's the other thing he keeps Yako around for.
* HumanityIsInsane: This is apparently why Neuro can't understand us: it's also something the manga spends a lot of time observing. It's also the reason HumansAreSpecial: since we're so insane and illogical, we can commit premedited crimes for really strong, twisted reasons, and it's that energy Neuro eats, [[spoiler:and why he won't let the New Bloodline destroy humanity.]]
* ICannotSelfTerminate: [[spoiler: HAL]]
* InTheBlood: The New Bloodline. Like humans in appearance, but they have evil intent in their genetic code, and see themselves as distinct from humanity in this respect.
* IronButtMonkey: Yako stays surprisingly intact even after being made Neuro's chewtoy, doesn't she?
** Same for Godai.
* JerkWithAHeartOfGold: Usui takes pride being a police and works hard fighting criminals. He is also shown to have respected Sasazuka, especially at the end when [[spoiler: Sasazuka dies.]] Neuro also qualifies. [[spoiler: When he was about to die, he questioned his own motive for protecting the humans: was it really just to save his food source? Also, Neuro kept Akane alive with a battery even when he had none to spare.]]
* {{Joshikousei}}: Yako.
* KarmaHoudini: To a certain extent, [[spoiler: Kasai, who managed to survive after having a burning building fall on top of him.]]
* KidDetective: Subverted in that although Yako is supposed to be the leader of the agency, in fact all the detective work is done by Neuro.
* KidWithTheLeash: [[BlatantLies Neuro tells]] [[spoiler:Sasazuka]] that Yako controls him and is taking terrible advantage. Their relationship seems like an inversion, but when Yako is serious [[spoiler:about no longer being a detective,]] she does what she wants.
* KillAllHumans: Manga only villain Sicks, to a T.
* LackOfEmpathy: Neuro ''is'' a demon, after all. The idea of giving a shit about what beings other than him want or feel generally does not occur to him.
* LethalChef: Yako's mother in the manga. Part of Yako's talent with cooking is to enable her to eat anything handy and the other part is allow her to have anything safe to eat. Her mother's food has both resulted in nitro-glycerin and radioactivity.
* LoveMakesYouEvil: [[spoiler: Professor Harukawa / HAL.]]
* MadArtist: Including a furniture designer who kills people who look down on furniture, a hair dresser who cuts off people's heads so he can style their hair and a stand-up comic who kills people because it's funny. There is also a singer who killed her friends to make her songs sound sadder, however she is one of the series sanest characters.
* MadBomber: "Histerrier"
* MadScientist: Professor Harukawa.
* {{Meitantei}}: Subverted: it may seem like Yako is a brilliant detective, but she's really a dense, and easily manipulated girl who owes Neuro a big favour.
** While she's not the true "brains" behind the operation, Yako slowly reveals superb talents at reading human intention that Neuro himself cannot match.
*** She herself becomes a Negotiator at the end of the manga; someone who can solve the mysteries in people's hearts; preferring to help the living instead of avenging the dead.
* MotiveRant: Happens with every single villain.
** But then turns into a ChekhovsGun of sort when they come across an arsonist who doesn't have a motive. [[spoiler: It indicated that he was under the influence of the Electronic Drug.]]
* {{Necromantic}}: HAL
* NoExportForYou: Though the anime was aired on Viz, it was not dubbed. The manga has also failed to come out in English.
* NukeEm: Referenced by Neuro. When he first arrived on Earth, a nuke wouldn't have put a scratch on him. Of course, by the time he's saying this, he's weakened enough that ordinary guns could kill him. Like the one the man he's talking to, who has tried to kill him before, has right there.
* ObfuscatingStupidity: Neuro acts like a puppet of Yako and speaks with a friendly accent in front of suspects... just before turning into a bird-headed monster that eats mysteries.
* OccultDetective: [[ExactlyWhatItSaysOnTheTin Who'dya think?]]
* OneHeadTaller: Yako is noticeably shorter than Neuro.
* OurDemonsAreDifferent: For one thing, demons find the human world extremely hazardous to their health, being destroyed completely after a few days. However, Neuro was able to live in the human world due to his AuthorityEqualsAsskicking trait
* OxygenMeter: Earth's atmosphere is poisonous to Neuro, constantly draining his health. He tries to breathe in miasma when he can, at the hot springs and [[spoiler:the village where Sai kidnaps Yako.]]
* ParasolOfPain: [=HIME=] in the anime
* PlayfulHacker: Higuchi who hacked into the Metropolitan Police Department's computers...and transformed their website into a department store website complete with replacing all of the departments and personal with lookalike shops and employees.
* PlayingAgainstType: Well... sort of. But come on - hearing Kana Ueda (who played serious [[{{Tsundere}} Rin Tohsaka]] in FateStayNight) play confused and victimized Yako is just plain hilarious.
* PlotSensitiveSnoopingSkills: Subverted, as Neuro is just as happy using his abilities to investigate the lives of his co-workers.
* PowerDegeneration: Neuro, becomes a plot point in the final arc when the enemies try to weaken him enough to kill him.
* ThePowerOfLove: In the manga, Neuro doesn't eat mysteries per se but the energy that would drive someone to do terrible, shameful, twisted things, knowing they're that wrong (otherwise, why try to hide them?). When he finally devoured the energy that caused the [[spoiler:creation of HAL and the entire HAL arc,]] there's so much of it he acts like he's sugar high.
** [[spoiler: Both Harukawa and HAL]] strive to bring back the woman they love, by making an electronic person with the former, and by hacking into other super-computers to create another electronic person from zero with the latter.
* PrehensileHair: Akane consists of nothing ''but'' living hair.
* PunnyName: A furniture dealer named Ikeya. I wonder if he's Swedish...
* PyroManiac: Kasai, and to a lesser extent his nephew [[spoiler: Homura.]]
* RedOniBlueOni: With Sasazuka as blue and Godai as red. The moment Yako sees how much they disagree, she compares them to water and oil.
* RedemptionEqualsDeath: In the manga, [[spoiler: Phantom Thief X/Sai, after landing a fatal blow onto Sicks.]]
* SadistTeacher: Apparently Neuro thinks that the best way to help Yako grow is to torture her.
* SealedEvilInACan: Err, box. And a red one at that!
* SelfMadeOrphan: Sicks is an extreme example, [[spoiler: he killed his mother at two years and his father at five.]]
* SerialKiller: Quite a few of the villains, some are quirky, but [[PersonOfMassDestruction those of the New Bloodline]] not so much.
* SeriousBusiness: Mysteries, for Neuro, which makes sense since he's starving to death and they're not his food, but they're evidence that the energy he eats should be present. This becomes a problem during the HAL and Sicks arcs, when crimes are being caused not by human twistedness but the electronic drug, biology, and so on. See NoMisterBondIExpectYouToDine.
* SharedUnusualTrait: All those possessed by the electronic drug have one red eye.
* SidekickExMachina: Neuro needed someone to the decoy for detective work, since people would understandably be worried about a demon running loose.
* SlidingScaleOfIdealismVersusCynicism: Some human beings are just plain evil: others are crazy and even a mild-mannered housewife can decide to [[spoiler:start planting bombs]]. Even good people can have disgusting obsessions and our minds are at the mercy of our biology (poor, poor Setsuna, not to mention Sai).
* SoLastSeason: Subverted, then inverted. While Neuro makes more use of the Seven Weapons during later arcs, they're not power-ups or new attacks but techniques he's had all along: they just weren't needed until now due to the SortingAlgorithmOfEvil. In fact, the reason he's using them isn't that he's gotten stronger but because [[spoiler:he's growing weaker as he starves to death, and he needs the most powerful spells in the demon world to do things he could have done with normal tools before.]] Turns out to be a double subversion, since the power that turns the tide in the last story arc is one that hasn't been a big deal before: [[spoiler:human allies.]]
* SpellMyNameWithAnS: X or Xi which is pronounced Sai.
** And on that note, i or Ai.
* SortingAlgorithmOfEvil: In the manga [[spoiler: you first have the regular murders, then ones who we find are being stirred up by Professor Harukawa's research. That leads to HAL, and then X takes on HAL's powers. Then finally Sicks shows up and sweeps X off the map with his minions are coming in order as well.]]
** Justified however in that Sicks send out his minions one after the other in order to weaken Neuros powers. If they had tried to team up on Neuro in the beginning he would have easily [[CurbStompBattle curbstomped]] them.
* TheStoic: Sasazuka is very calm [[{{NotSoStoic}} most of the time]]. Neuro, too, can arguably be in this trope, because he hardly ever loses his cool when fighting with villains even while many humans are in danger.
** NotSoStoic: [[spoiler:Sasazuka,]] when he finds out his family's murderer.
* SurprisinglyGoodEnglish: Seriously. Not even one "spilled" R. The fact that a word is mispelled in English is a plot point, even.
* {{Takehito Koyasu}}: as Neuro, who else?
* [[spoiler:ThouShaltNotKill: Despite how much Neuro forces Yako into(torture, bondage, general punishment, so on), Neuro has never once taken a life. His belief is that, even if a human has created a puzzle before, if they're left alive they can create more.]]
** [[spoiler: [[TechnicalPacifist However, when dealing with Sicks, he doesn't have this belief holding him back, considering that one, he poses a big threat to his feeding source if he survives and two he's far too monstrous to be forgiven.]]]]
* TrainingFromHell: In hindsight, ''everything Neuro does to Yako.''
* TransformationSequence: When a culprit is revealed he/she undergoes one of these. YMMV with how well it works, as some people consider it to be rather [[{{Narm}} narmy.]] However, this happens more frequently in the anime and in later chapters than at the beginning.
* UnholyMatrimony: X and Ai are a cute couple...when you get past all the killing.
* VillainProtagonist: [[EldritchAbomination Reality-warping, mind-screwing monster protagonist]], no less. Thankfully, Neuro has nothing to gain from harming humans, so the worst you can usually see from him is ComedicSociopathy towards Yako and other unfortunates.
* TheVirus: The electronic drug. It hacks the victim's mind [[spoiler:and finds something to exaggerate in order to make them useful to HAL. For instance, a childhood fondness for digging holes in the sand becomes an obsession with making holes in people.]]
* WallCrawl: Neuro makes gravity his bitch on regular basis, even sleeping on ceilings.
* WhamEpisode: [[spoiler: Sasazuka's death at the hands of Sicks.]]
* {{Xenofiction}}: The series spends a lot of time exploring just how alien Neuro is, and both his value system and biology are extremely important to the plot.
* YouAreNumberSix: Sicks; as well as Setsuna.[[note]]The number closest to zero. "Setsuna" is pronounced the same as the Japanese way for saying one over a billion; it's also commonly used to say, in Japanese, "an instant".[[/note]]
* YourFavorite: Yako and Sicks, both to Neuro.
** Instead of giving Neuro chocolates for Valentine's, Yako gives him [[spoiler:the wrapping paper. Which is made up of leads to potential mysteries, what he actually eats.]] It's a CMOA for Yako, that's she's grown to understand him so well, as well as a CMOH.
** Sicks invites Neuro to meet with him, and [[spoiler:tries to arrange a meal for him by forcing several people to kill, right there, by threatening their families and so on. He's wrong in that it's not the mystery itself Neuro eats, but the psychic energy of the motivation behind it, the twistedness that would drive someone to commit murder and try to hide it. Sicks's sick little tableau was the equivalent of offering a starving man Syrup of Ipecac. And then, since they hadn't pleased Neuro, he killed all of them, meaning that they would never be able to produce a real mystery]]. At that point, the reader learns how Neuro acts when he's really, really angry.
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