[[quoteright:200:http://static.tvtropes.org/pmwiki/pub/images/no-6_5922.jpg]]
[[caption-width-right:200:The main characters: [[NaiveNewcomer Shion]] and [[NobleDemon Nezumi.]]]]
In a high-class segregated society TwentyMinutesIntoTheFuture, the [[ChildProdigy young genius]] Shion helps a convicted boy escape from the soldiers pursuing him, resulting in Shion's subsequent demotion and loss of his special privileges. Four years later, he finds himself serving in the maintenance crew of the city park, until events conspire for the two to meet again, kicking off a series of events that cause Shion to question everything he has ever been told about the city he calls home -- [[{{Dystopia}} No. 6.]]

An anime series based on the original light novels was part of the Summer 2011 {{Noitamina}} Lineup, courtesy of StudioBONES. There is also a manga series drawn by Kino Hinoki.

Oh, and do note that, despite [[NamesTheSame the similarities in name]], [[DoNotConfuseWith the story has nothing to with]] [[Anime/BlueSubmarineNo6 a certain Blue Submarine fleet]].

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!!Tropes:
* AfterTheEnd: Atomic warfare has left us with only six habitable city-states.
* ApocalypseHow: Wide-scale Class 0 at first, with only a handful of cities with modern infrastructure and quality living conditions left. Later, No. 6 experiences [[spoiler: GaiasVengeance, thanks to meddling with a powerful forest entity that dishes out revenge in the form of killer bees]].
* AsceticAesthetic: The sectors, though the only one seen in-depth is No. 6 itself. Comes with being TwentyMinutesIntoTheFuture.
* BecauseYouWereNiceToMe : If Shion never saved Nezumi that night...
* TheBadGuyWins: Shion wanted to create a vaccine to protect people from the wasps but did not make it in time. [[spoiler: The EldritchAbomination that created the wasps got what it wanted but in the end results in a good ending.]]
* BerserkButton: Whatever you do, don't insult the Dogkeeper's mom. Or suggest that Nezumi become a prostitute. You will suffer endlessly.
** Don't forget, never harm Nezumi. [[spoiler:Or you'll get a bullet to the brain from Shion.]]
* BigBrotherIsWatching
* TheBigDamnKiss: Shion kisses Nezumi halfway through the series; in the final episode [[spoiler:Nezumi returns the favor before he leaves]].
** TonightSomeoneKisses: The Shion-to-Nezumi kiss is implied in the preview for that episode.
* BittersweetEnding: [[spoiler: In the anime, at least.]]
* ABoyAndHisX: Nezumi and his mice; Dogkeeper and her dogs.
* [[spoiler:BoysLoveGenre]]
* [[spoiler: BuryYourGays:]] [[SubvertedTrope Subverted]] at the last minute. [[spoiler: Shion dies and a wounded Nezumi [[TogetherInDeath is ready to join him]], but [[DeusExMachina intervention]] from Safu and Elyurias brings Shion BackFromTheDead and they escape the Correction Facility together]].
* ChildProdigy: Shion is one of many in No. 6. Per the novel, children are tested at two and those that have the highest intelligence are given the best living conditions and the brightest future.
* ColorCodedForYourConvenience: Shion's white / silver hair and Nezumi's black / dark grey hair set them as a yin-yang pair.
* CompressedAdaptation: Nine novels squeezed into eleven episodes. For the first eight or so episodes, the series appears to be an effective AdaptationDistillation, but as the climax approaches it becomes obvious how much information had to be left out.
* CrypticBackgroundReference: Not much information is given about the war and its consequences.
* CuteMachines: [[spoiler: Awww, look at that little mouse... [[RoboticReveal wait a minute.]]]]
** In the anime, the cleaning robots such as Sampo. Cute, colorful animal-shaped robots that clean and monitor public parks.
* CreatureOfHabit: Most occupants of No.6.
* DoYouWantToCopulate: "[[CrowningMomentOfFunny I want to have your sperm]]."
* {{Dystopia}}: No. 6 might seem pretty nice at first, but it keeps the peace at a price.
* EmpireWithADarkSecret
* EverythingsBetterWithRainbows: The opening has one.
* EverythingsWorseWithBees: Very, very much worse.
* GaiasLament: Nuclear warfare has decimated the environment, leading to only a few habitable pockets of civilization.
* [[spoiler:GaiasVengeance: ...and the abuse of the nature spirit Elyurias provokes her into bringing this at the end.]]
* GratuitousEnglish: Almost all the text in the anime, other than messages between characters, is in English. Several characters also pepper their speech with English phrases.
* [[spoiler: GovernmentConspiracy:]] [[spoiler:No.6's government will go to great lengths to maintain their utopia...]]
* HeadbuttThermometer: Shion to Nezumi.
* HeroicBSOD: Shion has one when his best friend gets bitten by one of the bees, and another one [[spoiler:when his best friend since childhood Safu, dies.]]
* HoldingHands: Shion and Nezumi. In bed, no less.
* IDidntMeanToTurnYouOn: [[HoYay Nezumi does this to Shion]] in volume 5 of the novel when talking about kissing him.
* [[IfYouKillHimYouWillBeJustLikeHim If You Kill Them You'll Be Just Like Them]]: Nezumi gets this speech when he expresses his desire for revenge against No. 6 in the cave during Episode 8.
* ImprovisedWeapon: In episode 4 Shion throws a mug at Rikiga's face.
* LecherousLicking: A top No 6 official licks a disguised Dogkeeper's neck, much to her disgust.
* LighterAndSofter: The Anime has taken out some of the more violent aspects of No. 6, especially character interactions and living conditions within the West Block.
* LockedIntoStrangeness: Shion begins with typical Japanese dark hair.
* LuminescentBlush: When Nezumi teases Shion about his little screaming fit. Shion turns completely red in embarrassment.
* MagicMusic: Nezumi and Safu both hear a particular song that causes them both to collapse. [[spoiler: It causes other strange things to happen, like causing a cave to glow and is supposed to be able to "calm" nature.]]
* MilkingTheGiantCow: Nezumi goes wild with his gestures in episode 3.
* MookChivalry: Expect any fight Nezumi gets into to have shades of this. [[spoiler: Although things get slightly more realistic towards the end of his fight with Inukashi's dogs.]]
* MotherNatureFatherScience: Invoked in the comparison between the scientific staff of the research facility and [[spoiler:Elyurias.]]
* NoPoverty: [[spoiler:At least in No.6 itself.]]
* NotTooDeadToSaveTheDay: [[spoiler:After Sion dies and a badly wounded Nezumi lies down to [[TogetherInDeath die with him]], Safu's spirit appears as Elyurias, heals Nezumi's wounds, [[BackFromTheDead resurrects Sion]] and destroys the wall around No. 6.]]
* [[spoiler: OfficialCouple: Nezumi and Shion were confirmed by the end of the series, to the delight of many YaoiFangirl's.]]
* PoorCommunicationKills: It really could -- it just doesn't have to kill the person that Nezumi doesn't want it to.
* [[spoiler: QueerRomance]]: Nezumi and Shion's relationship is a major theme of the story, if not its focus.
* [[spoiler: RapidAging:]] [[spoiler:To the unfortunate wasp hosts...]]
* {{Room 101}} : [[spoiler: The Correctional Facility]]
* RuleOfCute: The anime has cute-ified animal-like service robots like penguins and elephants that roll around the park picking up trash. In the novels and manga, the cleaning 'bots are just ordinary, cliche robots lacking much personality.
* SceneryPorn
* ShipTease: Sion and Nezumi.
* ShirtlessScene: Nezumi gets one at the beginning of Episode 3. So does Shion later on.
* ShmuckBait: doubles as a shout out to Shion's job when Nezumi uses [[spoiler:a Walker robot in episode 2 to stop the police car. It's perfectly in the middle of the road, in the middle of nowhere, where it has no business of being. Of course [[TooDumbToLive the cops get out of the car]] and [[CurbStompBattle get taken out one by one]] by Nezumi.]]
* ShootTheHostage: In episode 10, [[spoiler:the guard captain does this to one of his own men when Nezumi holds him hostage.]]
* ShownTheirWork: The author actually does take the trouble to write intelligent dialogue about brain synapses, basic human biology, the life cycle of hornets, etc, when the characters talk. Since, you know, this society's ranking is based on IQ, and Shion is supposed to be up there at the very top. As for the fuzzy bits, well, let's just write that off to ArtisticLicense.
* SkywardScream: A non-angsty example; Shion during the storm.
* [[SpoilerOpening Spoiler Ending]]: The ending sequence shows Shion [[spoiler:with white hair, unlike in the first two episodes]] and Nezumi [[spoiler:appearing to be older than Shion, unlike in the first episode]]. [[spoiler: The [[http://paste.plurk.com/show/628049/ song lyrics]] are even worse, spoiling how the story ends.]]
* [[spoiler: SyntheticPlague]]: All signs point to [[spoiler: The Birth of the Wasp]] being this.
* TakeAThirdOption: Shion has a bit of a genre savvy moment and suggests this, [[spoiler: saying if the walls around No. 6 are destroyed, there would essentially be no "them" and "us", effectively terminating the city as a separate entity.]] Nezumi is prompt to label this suggestion as bullpoopy.
* TheCavalry: [[spoiler: Nezumi coming to Shion's rescue in episode 2.]]
* TheParalyzer: Nezumi seems to like this move.
* TinCanRobot: The Walker robots who pick up trash. Shion has names for them as well.
* TheWallAroundTheWorld: The city of No. 6 is surrounded by a wall.
* TheseHandsHaveKilled / WhatHaveIDone: [[spoiler: See BerserkButton]]
* UncannyVillage: No. 6, of course. Where [[BlatantLies everyone is always happy and people all die painlessly with the same serene expression on their face.]]
* UrbanSegregation : You have Kronos, the elite district, Lost Town as the normal district, and finally the Western Block, which is the slums.
* WasItAllALie: Sion asks this after he and Nezumi [[spoiler: run away, leaving Safu to die in an explosion.]]
* WhatBeautifulEyes: In the novel, Shion almost cannot mention Nezumi without talking about how beautiful his eyes are.
* WindTurbinePower
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