No. 6

In a high-class segregated society Twenty Minutes Into the Future, the 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 -- No. 6.

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

English translations in process for the light novels can be found here.

Oh, and do note that, despite the similarities in name, the story has nothing to with a certain Blue Submarine fleet.

Tropes used in No. 6 include:

A Boy and His X: Nezumi and his mice; Dogkeeper and her dogs.
After the End: Atomic warfare has left us with only six habitable city-states.
Apocalypse How: Wide-scale Class 0 at first, with only a handful of cities with modern infrastructure and quality living conditions left. Later, No. 6 experiences Gaia's Vengeance, thanks to meddling with a powerful forest entity that dishes out revenge in the form of killer bees.
Ascetic Aesthetic: The sectors, though the only one seen in-depth is No. 6 itself. Comes with being Twenty Minutes Into the Future.
Because You Were Nice to Me : If Shion never saved Nezumi that night...
Berserk Button: 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. Or you'll get a bullet to the brain from Shion.
Big Brother Is Watching
The Big Damn Kiss: Shion kisses Nezumi halfway through the series; in the final episode Nezumi returns the favor before he leaves.
- Tonight Someone Kisses: The Shion-to-Nezumi kiss is implied in the preview for that episode.
Bittersweet Ending: In the anime, at least.
Boys Love Genre
Child Prodigy: 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.
Color Coded for Your Convenience: Shion's white / silver hair and Nezumi's black / dark grey hair set them as a yin-yang pair.
Compressed Adaptation: Nine novels squeezed into eleven episodes. For the first eight or so episodes, the series appears to be an effective Adaptation Distillation, but as the climax approaches it becomes obvious how much information had to be left out.
Cute Machines: Awww, look at that little mouse... wait a minute.
- In the anime, the cleaning robots such as Sampo. Cute, colorful animal-shaped robots that clean and monitor public parks.
Creature of Habit: Most occupants of No.6.
Dead Ex Machina: After Sion dies and a badly wounded Nezumi lies down to die with him, Safu's spirit appears as Elyurias, heals Nezumi's wounds, resurrects Sion and destroys the wall around No. 6.
Dystopia: No. 6 might seem pretty nice at first, but it keeps the peace at a price.
Empire with a Dark Secret
Everything's Better with Rainbows: The opening has one.
Everything's Worse with Bees: Very, very much worse.
Gaia's Lament: Nuclear warfare has decimated the environment, leading to only a few habitable pockets of civilization.
Gaia's Vengeance: ...and the abuse of the nature spirit Elyurias provokes her into bringing this at the end.
Gratuitous English: "DEREGISTRATION -- Cross out somebody's name from the list because of suspicion of murder"
Government Conspiracy: No.6's government will go to great lengths to maintain their utopia...
Headbutt Thermometer: Shion to Nezumi.
Ho Yay: Has its own page now -> No 6 Though all null, since the main duo's attraction and deep emotional attachment is canon. Invoked
Holding Hands: Shion and Nezumi. In bed, no less.
I Didn't Mean to Turn You On: Nezumi does this to Shion in volume 5 of the novel when talking about kissing him.
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.
Improvised Weapon: In episode 4 Shion throws a mug at Rikiga's face.
Lecherous Licking: A top No 6 official licks a disguised Dogkeeper's neck, much to her disgust.
Lighter and Softer: The Anime has taken out some of the more violent aspects of No. 6, especially character interactions and living conditions within the West Block.
Luminescent Blush: When Nezumi teases Shion about his little screaming fit. Shion turns completely red in embarrassment.
Magic Music: Nezumi and Safu both hear a particular song that causes them both to collapse. It causes other strange things to happen, like causing a cave to glow and is supposed to be able to "calm" nature.
Milking the Giant Cow: Nezumi goes wild with his gestures in episode 3.
Mook Chivalry: Expect any fight Nezumi gets into to have shades of this. Although things get slightly more realistic towards the end of his fight with Inukashi's dogs.
Mother Nature, Father Science: Invoked in the comparison between the scientific staff of the research facility and Elyurias.
No Poverty: At least in No.6 itself.
Poor Communication Kills: It really could -- it just doesn't have to kill the person that Nezumi doesn't want it to.
Rapid Aging: To the unfortunate wasp hosts...
Room 101 : The Correctional Facility
Rule of Cute: 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.
Scenery Porn
Ship Tease: Sion and Nezumi.
Shirtless Scene: Nezumi gets one at the beginning of Episode 3. So does Shion later on.
Shmuck Bait: doubles as a shout out to Shion's job when Nezumi uses 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 the cops get out of the car and get taken out one by one by Nezumi.
Shoot the Hostage: In episode 10, the guard captain does this to one of his own men when Nezumi holds him hostage.
Shown Their Work: 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 Artistic License.
Skyward Scream: A non-angsty example; Shion during the storm.
Spoiler Ending: The ending sequence shows Shion with white hair, unlike in the first two episodes and Nezumi appearing to be older than Shion, unlike in the first episode. The song lyrics are even worse, spoiling how the story ends.
Synthetic Plague: All signs point to The Birth of the Wasp being this.
Take a Third Option: Shion has a bit of a genre savvy moment and suggests this, 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.
The Cavalry: Nezumi coming to Shion's rescue in episode 2.
The Paralyzer: Nezumi seems to like this move.
Tin Can Robot: The Walker robots who pick up trash. Shion has names for them as well.
The Wall Around the World: The city of No. 6 is surrounded by a wall.
Uncanny Village: No. 6, of course. Where everyone is always happy and people all die painlessly with the same serene expression on their face.
Urban Segregation : You have Kronos, the elite district, Lost Town as the normal district, and finally the Western Block, which is the slums.
Was It All a Lie?: Sion asks this after he and Nezumi run away, leaving Safu to die in an explosion.
What Beautiful Eyes!: In the novel, Shion almost cannot mention Nezumi without talking about how beautiful his eyes are.
Wind Turbine Power