History Manga / ArpeggioOfBlueSteel

* CryCute: [[spoiler:Kongou, of all people, in episode 12. When Iona finally reaches her core, Kongou is sitting down with her face buried by her knees, with tears streaming down.]]

* AluminiumChristmasTrees: Apart from rocket propelled torpedoes, the JMSDF attack submarine ''Hakugei'' has a rocket propulsion engine. DARPA has been researching adapting rockets to submarines for the last 10 years.

* CoolShip: This whole manga is an ode to cool ships of UsefulNotes/WorldWarII, rebuilt with incredibly advanced capabilities. The Japanese-built Hakugei 3 deserves special mention for being the one human ship capable of facing the Fleet of Fog and surviving. Thanks to its modular construction it can be quickly refitted for very different abilities, like the LightningBruiser Assault Mode and the stealthy, long-range Cruiser Mode.

* DecoyConvoy: [[spoiler:Iona]] takes the vibration torpedo plans from the government, but secretly transfers them to [[spoiler:the Hakugei]] while at sea, before going off to openly fight the Fleet of Fog. There are two reasons for this. First, the open battles have a chance of loosening the blockade on Japan while diverting attention from the real convoy, and second, [[spoiler:having the first human-made anti-Fog weapon be delivered by a human-made and crewed submarine would be a far greater boost to world morale than having a rogue Fog submarine do the job.]]

* DidYouJustPunchOutCthulhu: The Hakugei III [[spoiler:becomes the first human made ship to sink not only one, but TWO Fleet of Fog battleships. Granted, they used stolen Fleet of Fog tech, but it was still a very big deal]].

** ''Hakugei'' uses a rocket engine to achieve supercavitation. This is [[http://www.spacewar.com/reports/Northrop_Grumman_Team_Selected_To_Evaluate_Supercavitation_Based_Underwater_Naval_Transport_999.html currently under research]] by [[http://en.wikipedia.org/wiki/DARPA DARPA]].

** The first act of the story concludes with a load of this. [[spoiler:Kongou has been sunk by I-401 using torpedo bombers and Hakugei can finally head to America. But 2nd Fleet has been reorganized under Hyuuga, who had been captured by Yukikaze alongside Hiei's core, taken to Yamato and given a rebuilt hull, and 1st Fleet under Nagato remains a concern to the vibration torpedo delivery mission. Gunzou was injured and subsequently went missing during the battle and was later revealed to be captured by the Fog and placed in their secret SpaceElevator facility to recover, a facility that is overseen by Choukai, Takao's younger sister and the first Heavy Cruiser that he and Iona sank. Finally, major events have been happening in Japan while the fight was underway, particularly at the Maritime Academy with multiple Mental Models trying to unravel or hide the Facility No. 4 Incident, including Yamato herself, with her other identity Kotono Amaha saying that she hoped Gunzou would reprimand her for what she would do next, hinting that they would meet each other in future.]]

* AdaptedOut: The fate so far of Kotono Amaha, Lawrence, the Hakugei, the mini Mental Models...

** [[spoiler:After all the teasing and hints, Chapter 116 finally reveals what started the Facility No. 4 Fire. It was ''Yamato'' herself who accidentally set fire to the Facility when she went to retrieve Kotono Amaha to be the Fog's new superordinate program, ostensibly to replace the Admiralty Code. As for where the Mental Models come from, it was Yamato's attempt to communicate with Kotono by copying her physical appearance, a process that was disseminated to the rest of the Fog which allowed their AIs to eventually become self-aware. For her part, Kotono willingly went along with Yamato, implying that she survived the fire, and has been helping the Fog for the past two years. Meanwhile, Yamato and Kotono had been working to revive the casualties of the Fire as a token of goodwill to Japan. The chapter ends with Makoto demanding to know if Kotono is still human and the Admiralty Code (named Gretel Hexe Andvari) making contact with the Izumo household in Japan.]]

* SpaceshipGirl: Fleet of Fog ships of heavy cruiser class and up (including the I-400 class submarines) can have a "Mental Model", which represents the AI controlling the ship. Unusually for this trope, Mental Models weren't intended to interact with a crew, but rather to help the ships to develop more [[WeakButSkilled human-like tactics and strategies]] through the imitation of human limitations and perspectives. The largest battleships with greater computation capabilities (i.e. Yamato, Nagato, Bismark) can have two, but only the former displayed distinct personalities between her two Mental Models while the latter two ships do not. Iona and Takao can also create [[FunSize miniature versions of themselves]] who have some measure of autonomy and can be used for shipboard tasks (or just be adorable).

** [[spoiler:After all the teasing and hints, Chapter 116 finally reveals what started the Facility No. 4 Fire. It was Yamato who accidentally set fire to the Facility when she went to retrieve Kotono Amaha to be the Fog's new superordinate program, ostensibly to replace the Admiralty Code, and Yamato copied Kotono's physical appearance to create her own Mental Model to properly communicate with her while Kotono herself willingly went along with Yamato after she was 'claimed by the Fog', implying that she survived the fire, and has been helping the Fog for the past two years. Meanwhile, Yamato and Kotono had been working to revive the casualties of the Fire as a token of goodwill to Japan. The chapter ends with Makoto demanding to know if Kotono is still human and the Admiralty Code (named Gretel Hexe Andvari) making contact with the Izumo household in Japan.]]
** [[spoiler:Chapter 121 brings us several revelations. Gretel's visit to the Izumo household reveals that Saori Chihaya, Gunzou's mother, was his descendant. Meanwhile, in the Straits of Gibraltar, Bismarck and a girl called Lord Archer reveal that the former was something else before being a battleship while the latter is about 100 years old and the UK's best-kept secret, was related to Gretel and she would somehow rectify Kotono's sin of giving individuality and humanity to the Fog AIs. Finally, Gretel appears before everyone within Facility No. 4 declaring that she will deliver her verdict upon the entire world as the Admiralty Code.]]

* ShoutOut: The music video for the opening song of ''Ars Nova'' has scenes shot in front of and aboard the JMSDF ship ''Kirishima''. In Episode 11, Kyouhei's reaction to seeing [[spoiler:Kongou]] is [[Franchise/StarWars "That's no battleship!"]]

* BlandNameProduct: [[http://mangafox.me/manga/aoki_hagane_no_arpeggio/v04/c023/5.html Jenga? Or Genius?]]

* ImagineSpot: In chapter 9 of the manga, Takao reads a children's book about sea captains. The result is... [[http://mangafox.me/manga/aoki_hagane_no_arpeggio/v02/c009/18.html Interesting.]]

Compare to ''VideoGame/KantaiCollection'', another series (with [[Anime/KantaiCollection its own anime adaptation]], to boot) that also features female personifications of World War 2 ships. The two franchises have collaborated on an in-game event for December 2013, which features characters from the ''Ars Nova'' anime assisting the girls from Kancolle against Kongou and Maya. See also ''VideoGame/AzurLane'', the same basic concept applied to a ShootEmUp mobile game (and an [[Anime/AzurLane anime adaptation]] of its own).

** A major part of the early story centers around the fact that even though I-401 has corrosion torpedoes that can damage Fleet of Fog warships, she doesn't have the capacity to replace the ones fired, and is running out. Also, the Japanese government has developed their own torpedo that can theoretically let humanity go back on the offensive, but they don't have the industrial capacity to build them in large quantities, so they need I-401 to take the last remaining prototype and a copy of the plans to America, which has large numbers of factories that can be retooled for such a purpose.

* FrickinLaserBeams: Standard weapons of the Fleet of Fog. Any gun seen on a Fog ship will shoot these rather than shells. Often abused as BeamSpam.

** Chapter 116 finally sheds some light on the matter. [[spoiler:Yamato explains to the three Japanese Prime Ministers that she started the Facility No. 4 fire when she went to retrieve Kotono Amaha to turn her into the Fog's superordinate system in the 100-year absence of the Admiralty Code. She created her own Mental Model based on Kotono's physical appearance to better communicate her intent to Kotono before disseminating the Mental Model program to the rest of the Fog (which might explain why all the Mental Models are female). Kotono herself willingly went along with Yamato and has aided the Fog since. Why she was chosen and whether or not she is still human remain to be seen.]]

* ShowWithinAShow: [[MagicalGirl Hisonic Miku-chan]], an anime popular with Makie Osakabe, Kyouhei and Iona.
* SpaceshipGirl: Fleet of Fog ships of heavy cruiser class and up (including the I-400 class submarines) can have a "Mental Model", which represents the AI controlling the ship. Unusually for this trope, Mental Models weren't intended to interact with a crew, but rather to help the ships to develop more [[WeakButSkilled human-like tactics and strategies]] through the imitation of human limitations and perspectives. The largest battleships with greater computation capabilities (i.e. Yamato, Nagato, Bismark) can have two, sometimes with distinct personalities from the other. Iona and Takao can also create [[FunSize miniature versions of themselves]] who have some measure of autonomy and can be used for shipboard tasks (or just be adorable).

* TeleportersAndTransporters: The Flagship-class equipment used by Kongou allows her to instantly transport subordinate vessels to her location through the use of the quantum communications network. The absurd power requirements to do so is acknowledged, as the system only teleports the ships' core (about the size of an apple) and then rebuilds their whole body from nanomaterial stocks. The ship bodies left behind are broken down for salvage.

* WalkDontSwim: The mental models of the Fog ships are fully capable of walking on the bottom of the ocean if they want to.

** The first act of the story concludes with a load of this. [[spoiler:Kongou has been sunk by I-401 using torpedo bombers and Hakugei can finally head to America. But 2nd Fleet has been reorganized under Hyuuga, who had been captured by Yukikaze alongside Hiei's core, taken to Yamato and given a rebuilt hull, and 1st Fleet under Nagato remains a concern to the vibration torpedo delivery mission. Gunzou was injured and subsequently went missing during the battle and was later revealed to be captured by the Fog and placed in their secret SpaceElevator facility to recover, a facility that is overseen by Choukai, Takao's sister and the first Heavy Cruiser that he and Iona sank. Finally, major events have been happening in Japan while the fight was underway, particularly at the Maritime Academy with multiple Mental Models trying to unravel or hide the Facility No. 4 Incident, including Yamato herself, with her other identity Kotono Amaha saying that she hoped Gunzou would reprimand her for what she would do next, hinting that they would meet each other in future.]]
** [[spoiler:After all the teasing and hints, Chapter 116 finally reveals what started the Facility No. 4 Fire. It was Yamato who accidentally set fire to the Facility when she went to retrieve Kotono Amaha to be the Fog's new superordinate program, ostensibly to replace the Admiralty Code, and Yamato copied Kotono's physical appearance to create her own Mental Model to properly communicate with her while Kotono herself willingly went along with Yamato after she was 'claimed by the Fog', implying that she survived the fire, and has been helping the Fog for the past two years. Meanwhile, Yamato and Kotono had been working to revive the casualties of the Fire as a token of goodwill to Japan. The chapter ends with Makoto demanding to know if Kotono is still human and the Admiralty Code making contact with Izumo in Japan.]]

* FrickinLaserBeams: Standard weapons of the Fleet of Fog. Nny gun seen on a Fog ship will shoot these rather than shells. Often abused as BeamSpam.

* EnemyCivilWar: The Fog Fleet isn't as unified an entity as it was a decade before, as the creation of Mental Models has given rise to individual personalities among its ships... and they don't always agree with each other. Depending on who you ask, there are as many as ''six'' different factions in the Fog Fleet alone, all with different aims and at times working at cross-purposes: of particular note, the Scarlet Fleet under ''Musashi'' and Shouzou Chihaya seek to weld the Fog with human crews, ostensibly to fulfill the Admiralty Code's unfinished orders; they are directly opposed by a faction under ''Hood'', who aims to stop Chihaya's ambition as usurping the Admiralty Code's authority.

* FrickinLaserBeams: Standard weapons of the Fleet of Fog, any gun seen on a Fog ship will shoot these rather than shells. Often abused as BeamSpam.

** Even the Fog have this, as certain ships of the Oriental and European[[note]]i.e. Pacific and Atlantic[[/note]] fleets hold subtle but distinct animosity toward each other. The best example of this is shown in recent chapters, [[spoiler:where ''I-402'', seemingly on orders from ''Yamato'', actively supported both ''Takao'' and ''I-401'' in fighting ''U-2501''. And before that, there were assorted scenes of Oriental ships not being keen on ''U-2501'''s presence in the pacific, nor Souzou Chihaya holding command of the European Fleet in general.]]

* LaserSight: Averted. The snipers are using infrared beam which are invisible to the human eye. This makes a lot more sense than optical lasers.
* MacGuffin: The series actually has two: The vibration torpedo which must be smuggled to the United States to be mass produced, and the "Admiralty Code" that the Fleet of Fog is looking for.
** LivingMacGuffin: Given how the Admiralty Code has been depicted as having a Mental Model of its own (a young woman wearing an old-style Apollo astronaut's rig), it could be seen as this as well.

* {{Nanomachines}}: Also commonly referred to as "nanomaterial", the Fleet of Fog is made entirely of the stuff and it's the source of all the GameBreaker technology they use. Where it all comes from is one of the many mysteries surrounding the Fog, but samples were found in sea water as early as the 1920s according to the [[AllThereInTheManual supplementary material]].

** The fire at Facility No.4 of the naval academy Gunzo went to. The only thing sure is that Kotono is [[NeverFoundTheBody supposed to have died there.]] Whatever happened there is important enough that by the end of act 1 ''3'' groups of mental models joined the Academy in an attempt to discover what exactly happened while at the same time interfering with the other groups' efforts to do the same.

** As does [[spoiler:Amaha Kotono, who is effectively Yamato's human twin and may or may not still be alive.]]

* OrcusOnHisThrone: The Fleet of Fog are shown to be perfectly capable of wiping out literally every coastal city on the planet (which basically means all of Japan). However, they're mostly content with just sitting back and maintaining the global blockade. Revealed by Yamato later on to be one of the orders given to the Fog Fleet by the Admiralty Code. Many among the Fog are now wondering ''why'' this is so.

* PaintingTheFourthWall : In chapter 18 Haruna gives Makie a full-body scan. Highlights include her brain, hands, hair and SpeechBubbles.

* PrettyLittleHeadshots: Completely averted. Objects, humans, [[spoiler: human decoys made of nanomaterial]] hit with high-velocity bullets practically [[PinkMist ''explode'']].

** Chapter 116 finally sheds some light on the matter. [[spoiler:Yamato explains to the three Japanese Prime Ministers that she started the Facility No. 4 fire when she went to retrieve Kotono Amaha to turn her into the Fog's superordinate system in the 100-year absence of the Admiralty Code. She copied Kotono's form to create her own Mental Model to communicate with her more effectively before disseminating the Mental Model program to the rest of the Fog (which might explain why all the Mental Models are female). Kotono herself willingly went along with Yamato and has likely aided the Fog since. Why she was chosen and whether or not she is still human remain to be seen.]]

** Chapter 116 finally sheds some light on the matter. [[spoiler:Yamato explains to the three Japanese Prime Ministers that she started the Facility No. 4 fire when she went to retrieve Kotono Amaha to turn her into the Fog's superordinate system in the 100-year absence of the Admiralty Code. She copied Kotono's form to create her own Mental Model to communicate with her more effectively before disseminating the program for it to the rest of the Fog (which might explain why all the Mental Models are female). Kotono herself willingly went along with Yamato and has likely aided the Fog since. Why she was chosen and whether or not she is still human remain to be seen.]]

** The first act of the story concludes with a load of this. [[spoiler:Kongou has been sunk by I-401 using torpedo bombers and Hakugei can finally head to America. But 2nd Fleet has been reorganized under Hyuuga, whom had been captured by Yukikaze and taken to Yamato and given a rebuilt hull, and 1st Fleet under Nagato remains a concern to the vibration torpedo delivery mission. Gunzou was injured and subsequently went missing during the battle and was later revealed to be captured by the Fog and placed in their secret SpaceElevator facility to recover, a facility that is overseen by Choukai, Takao's sister and the first Heavy Cruiser that he and Iona sank. Finally, major events have been happening in Japan while the fight was underway, particularly at the Maritime Academy with multiple Mental Models trying to unravel or hide the Facility No. 4 Incident, including Yamato herself, with her other identity Kotono Amaha saying that she hoped Gunzou would reprimand her for what she would do next, hinting that they would meet each other in future.]]
** [[spoiler:After all the teasing and hints, Chapter 116 finally reveals what started the Facility No. 4 Fire. It was Yamato who accidentally set fire to the Facility when she went to retrieve Kotono Amaha to be the Fog's new superordinate program, ostensibly to replace the Admiralty Code, and Yamato copied Kotono's physical appearance to create her own Mental Model. Kotono herself willingly went along after she became 'one with the Fog', implying that she survived the fire, and had helped the Fog for the past two years. Meanwhile, Yamato and Kotono had been working to revive the casualties of the Fire as a token of goodwill to Japan. The chapter ends with Makoto demanding to know if Kotono is still human and the Admiralty Code making contact with Izumo in Japan.]]

** [[spoiler:After all the teasing and hints, Chapter 116 finally reveals what started the Facility No. 4 Fire. It was Yamato who accidentally set fire to the Facility when she went to retrieve Kotono Amaha to be the Fog's new superordinate program, ostensibly to replace the Admiralty Code, and Yamato copied Kotono's physical appearance to create her own Mental Model. Kotono herself willingly went along after she became 'one with the Fog', implying that she survived the fire. Meanwhile, she had been working for the past two years after the Fire to revive the casualties as a token of goodwill and bargaining chip to Japan.]]

* CozyCatastrophe: There are a few countries that are managing all right despite the global blockade, either because they're large enough to be self-sufficient or have neighbors with land borders they can trade with.
* CrapsackWorld: The current situation is strangling Japan to death economically (see Easy Logistics), and Europe is in the midst of a major war. One way or another, every nation on Earth is feeling the effects of the blockade.

* DecoyConvoy: [[spoiler:Iona]] takes the vibration torpedo plans from the government, but secretly transfers them to [[spoiler:White Whale]] while at sea, before going off to openly fight the Fleet of Fog. There are two reasons for this. First, the open battles have a chance of loosening the blockade on Japan while diverting attention from the real convoy, and second, [[spoiler:having the first human-made anti-Fog weapon be delivered by a human-made and crewed submarine would be a far greater boost to world morale than having a rogue Fog submarine do the job.]]

** Ashigara and Haguro are dragooned into joining Iona's crew after losing their ships [[spoiler: and saving Iori's life]]. They part on good terms later.

* EvolvingCredits: Each episode of the anime features brief clips of that episode's contents during the opening credits. Additionally, Kirishima's teddy bear shows up when she's shown onscreen during the opening after she gains control of it. The compilation volumes for the manga have their own version: each volume adds another character to the group shot on the back cover, usually someone introduced that volume.

** In-universe, the weapons, armor and shielding of the Fleet of Fog fall right into this trope. Humanity's combined fleets couldn't put a dent in them 17 years ago.
** Before the Fog showed up, it was the introduction of practical supercavitating torpedoes. Torpedoes capable of going more than 300 knots rendered conventional naval design and tactics obsolete almost overnight. Ironically, in the real world, supercavitating torpedoes aren't yet gamebreakers, as their high speed is achieved at the expense of target tracking ability (the Shkval is an unguided torp) and range - 13km for the [[http://en.wikipedia.org/wiki/VA-111_Shkval VA-11 Shkval]], vs 38km for the [[http://en.wikipedia.org/wiki/ADCAP ADCAP]].

** The RealLife battleship ''Bismarck'' had always been explicitly referred to as a 'he' by its commander Capt. Ernst Lindemann and the Kriegsmarine. It still has twin girls as mental models.
** HandWaved also in that the Mental Models explain this has to do with the fact that humanity almost always treat ships as feminine, and using female pronouns when referring to them. That's apparently the only justification they have, and it's not delved into any further.
* GodzillaThreshold: Humanity has reached such a desperate point that they're willing to try anything in an attempt to fight off the Fog ships. Japan in particular has evidently suspended some human rights in order to relocate or just abandon certain parts of its population and later engineered select ArtificialHumans to handle such decisions in future.
* GravityMaster: Given the feats displayed by Haruna without the assistance of her ship, all Fog mental Models are probably this as standard. Also combines with BarrierWarrior and VoluntaryShapeshifting.
* {{Hammerspace}}: Played with on the Fog Fleet ships. It's for the most part averted, and justified in that while they look like WWII-era ships, that is merely on the outside. With no need to concern themselves with crews, the ships can devote more space to armament, munitions, and power supply.[[note]]This is shown in flashback scenes when ''I-401'' Iona first awoke to become Gunzou's ship, the bridge and engine room were much more sparse than it is during the series proper[[/note]] Other aspects of the ships' armament are explained as the ships using [[{{Nanomachines}} Nanomaterials]] to alter themselves or their armaments on the fly[[note]]The main batteries can convert between a solid shell mode for classic-style cannon bombardment, and a high energy laser/beam by popping open the barrel and turret armor. Use of Gravity Canon modes, often shows the ship popping open to create a WaveMotionTuningFork with the hull. Though Iona's an exception, as her's is basically a giant turbine stored in the bow of the ship.[[/note]] That said, their solid munitions play this straight, with the surface ships simply popping open more missile tubes as needed. Ammunition storage is only mentioned when needed for drama for the most part.
* HumanityIsInfectious: More or less the main aesop of the series. Whether a Fog vessel decides to aid the Blue Steel crew or antagonize them, they will inevitably GrowBeyondTheirProgramming and no longer follow the Admiralty Code's directives - unless they flat out refuse to understand, in which case they wouldn't develop a personality to begin with, and so can be fought without much sympathy.

* ThePiratesWhoDontDoAnything: Because aircraft are too small to mount Klein Fields or other GameBreaker tech, air defense is the one area where humanity can actually defeat the Fleet of Fog. As a result aircraft carriers like Zuikaku have lost most or all of their planes and are stuck being ''really bored''. Zuikaku herself passes the time by fishing and cooking what she catches.

** Both Kamikage and the Prime Minister are willing to help the I-401 in any way they can, especially when a large portion of the Japanese government is out to try and thwart their plans.
** Makoto Osakabe, the minister of Hokkaido, is perfectly willing to let Haruna, Kirishima, and Maya be, though he does admit that he will eventually have to put on a token amount of resistance to save face once they are ready to leave port.
* TheReveal: [[spoiler:Yamato's]] mental models are the spitting image of [[spoiler:Kotono Amaha, one of Gunzou Chihaya's supposedly dead ChildhoodFriends and likely love interest]]. Made all the more effective by introducing [[spoiler: Yamato]] first and leaving [[spoiler: Kotono's]] appearance vague until the reveal in Chapter 23.
** Chapter 116 finally sheds some light on the matter. [[spoiler:Yamato explains to the three Japanese Prime Ministers that she started the Facility No. 4 fire when she went to retrieve Kotono Amaha to turn her into the Fog's superordinate system in the 100-year absence of the Admiralty Code. She copied Kotono's form to create her own Mental Model to communicate with her more effectively before disseminating the program for it to the rest of the Fog. Kotono herself willingly went along with Yamato and has likely aided the Fog since. Why she was chosen and whether or not she is still human remain to be seen.]]

** Battlecruiser Repulse's mental model is an English maid. She takes the maid persona so far that she actually repairs her battle damage by ''sweeping'' it with brooms.
** Vampire's mental model follows the same theme as her flagship, except in a child-sized short skirt version. This is coupled with some appropriate vampire themes, namely CuteLittleFangs and a bat-shaped pendent on her uniform collar. Overall she looks like something out of a Creator/TimBurton movie.

* SuperweaponSurprise: The Flagship-class equipment that the Fog store in Low-Earth Orbit. Other than opening up question on Fog space-based facilities, their origins are a mystery even to the Fog.

* TransformingMecha: The Fog Fleet ships are all replicas of WWII warships, but only on the outside--[[spoiler:under that is their advanced weaponry that they rearrange on the fly]].

* WaveMotionGun: While the Fleet of Fog on the whole has dramatically superior armaments and shielding to the human fleets, Heavy Cruisers and larger have access to Super-Heavy Cannons that are exactly this. Battleship-class vessels come equipped with 'Super Gravity Cannons', which despite the name fill the trope nicely, since the weapon tends to ''bend space around it and its firing path''.

** The first act of the story concludes with a load of this. [[spoiler:Kongou has been sunk by I-401 using torpedo bombers and Hakugei can finally head to America. But 2nd Fleet has been reorganised under Hyuuga, whom had been captured by Yukikaze and taken to Yamato and given a rebuilt hull, and 1st Fleet under Nagato remains a concern. Gunzou was injured and subsequently went missing during the battle and was later revealed to be captured by the Fog and placed in their secret SpaceElevator facility to recover, a facility that is overseen by Choukai, Takao's sister and the first Heavy Cruiser that he and Iona sank. Finally, events have been happening in Japan. particularly the Maritime Academy with multiple Mental Models trying to unravel or hide the Facility No. 4 Incident, including Yamato herself, with her other identity Kotono Amaha saying that she hoped Gunzou would reprimand her for what she would do next, hinting that they would meet each other in future.]]
* WhatMeasureIsANonHuman: Gunzou's acceptance of Iona and other Mental Models as people forms the core of his strategy for dealing with the Fleet of Fog as a whole: if a Mental Model allows a Fog ship to think like a human, they can be ''negotiated with''. His bluffing Takao into surrendering was a trial run of his theory. Ultimately he hopes humanity and the Fog can reach a negotiated cease-fire (using the Vibration Torpedo as a bargaining chip so humanity can negotiate from a position of relative parity), a concept which is starting to spread.

* ImprovisedPlatform: Klein Fields can be manipulated to be used like this.

* BrokenRecord: [[spoiler:Maya spouts off repeated lines after TheReveal in episode 10.]]

* WhamEpisode: Quite a few happen over the course of the story, often leaving more questions than answers.
** The first act of the story concludes with a load of this. [[spoiler:Kongou has been sunk by I-401 using torpedo bombers and Hakugei can finally head to America. But 2nd Fleet has been reorganised under Hyuuga, whom had been captured by Yukikaze and taken to Yamato and given a rebuilt hull, and 1st Fleet under Nagato remains a concern. Gunzou was injured and subsequently went missing during the battle and was later revealed to be captured by the Fog and placed in their secret SpaceElevator facility to recover, a facility that is overseen by Choukai, Takao's sister and the first Heavy Cruiser that he and Iona sank. Finally, events have been happening in Japan. particularly the Maritime Academy with multiple Mental Models trying to unravel or hide the Facility No. 4 Incident, including Yamato herself, with her other identity Kotono Amaha saying that she hoped Gunzou would reprimand her for what she would do next, hinting that they would meet each other in future.]]

* ThePiratesWhoDontDoAnything: Because aircraft are too small to mount Klein Fields or other GameBreaker tech, air defense is the one area where humanity can actually defeat the Fleet of Fog. As a result aircraft carriers like Zuikaku have lost most or all of their planes and are stuck being ''really bored''. Zuikaku herself passes the time by fishing and cooking what she catches.

* OrcusOnHisThrone: The Fleet of Fog are shown to be perfectly capable of wiping out literally every coastal city on the planet (which basically means all of Japan). However, they're mostly content with just sitting back and maintaining the global blockade. Revealed by Yamato later on to be one of the orders given to the Fog Fleet by the Admiralty Code. Many among the Fog are now wondering ''why'' this is so.

* CreepyChild:
** Iona has occasional shades of this. [[spoiler:This effect is amplified with the mental models of 400 and 402.]] Completely averted with Iona and Takao's mini versions, who are moe incarnate.
** Invoked with Musashi, especially in chapter 48.

* ArmorPiercingAttack: Corrosive Torpedoes are able to penetrate Klein Fields.

Compare to ''VideoGame/KantaiCollection'', another series (with [[Anime/KantaiCollection its own anime adaptation]], to boot) that also features female personifications of World War 2 ships. The two franchises have collaborated on an in-game event for December 2013, which features characters from the ''Ars Nova'' anime assisting the girls from Kancolle against Kongou and Maya. See also ''VideoGame/AzurLane'', the same basic concept applied to a ShootEmUp mobile game.

** Chapter 116 finally sheds some light on the matter. [[spoiler:Yamato explains to the three Japanese Prime Ministers that she started the Facility No. 4 fire when she went to retrieve Kotono Amaha to turn her into the Fog's superordinate system in the 100-year absence of the Admiralty Code. She copied Kotono's form to create her own Mental Model to communicate with her more effectively before disseminating the program for it to the rest of the Fog. Kotono herself willingly went along with Yamato and has likely aided the Fog since.]]

** The first act of the story concludes with a load of this. [[spoiler:Kongou sunk and 2nd Fleet reorganised under Hyuuga, whom had been captured by Yukikaze and taken to Yamato and given a rebuilt hull. Gunzou went missing during the battle and was later revealed to be captured by the Fog and placed in their secret SpaceElevator facility to recover, one that is overseen by Choukai, the first Heavy Cruiser he and Iona sank. Finally, events have been happening in Japan. particularly the Maritime Academy with multiple Mental Models involved trying to unravel or hide the Facility No. 4 Incident, including Yamato herself, with her other identity Kotono Amaha saying that she hoped Gunzou would reprimand her for what she would do next, hinting that they would meet each other in future.]]

** Yamato gives off this vibe, what with being a YamatoNadeshiko.

* TheReveal: [[spoiler:Yamato's]] mental models are the spitting image of [[spoiler:Kotono Amaha, one of Gunzou Chihaya's supposedly dead ChildhoodFriends and likely love interest]]. Made all the more effective by introducing [[spoiler: Yamato]] first and leaving [[spoiler: Kotono's]] appearance vague until the reveal.
** [[spoiler:Chapter 116 reveals what happened to her, with Yamato explaining how she caused the Facility No. 4 fire when she went to retrieve Kotono Amaha to become the Fog's superordinate system in the absence of the Admiralty Code and copied Kotono's form to create her own Mental Model. Kotono herself went along with it willingly.]]

** Battlecruiser Repulse's mental model is an English maid. She takes the maid persona so far that she actually repairs her battle damage by ''sweeping''.

** On one side in the Japanese government is Assistant Secretary Ryuujirou Kamikage who wants to use the I-401 to transport their most successful man-made weapon that is capable of destroying a Fleet of Fog ship to the United States, so it can be mass produces, and has the support of the Japanese Navy and the local US forces. On the other side is the powerful Tycoon and top candidate for Prime Minister Ryoukan Kita, who wants the I-401 returned back to the Japanese Government so they can reverse engineer it and make their own Fleet of Fog ships, and who has strong contacts withing the Japanese Army.
** At one point, an Army company under Kita's influence seizes the I-401's dock and arrests the crew; the Navy [=SEALs=] came ''very'' close to starting a firefight and rescuing the crew by force, before both sides were ordered to stand down.

** Vampire's mental model follows the same theme as her flagship, except in a child-sized short skirt version. This is coupled with some appropriate vampire themes, namely CuteLittleFangs and a bat shaped pendent on her uniform collar. Overall she looks like something out of a Creator/TimBurton movie.

* ShoutOut: All of the Fleet of Fog ships are replicas of real life WWII era warships, all part of the OntologicalMystery surrounding their origin.

* SpaceshipGirl: Fleet of Fog ships of heavy cruiser class and up (including the I-400 class submarines) can have a "Mental Model", which represents the AI controlling the ship. Unusually for this trope, Mental Models weren't intended to interact with a crew, but rather to help the ships to develop more [[WeakButSkilled human-like tactics and strategies]] through the imitation of human limitations and perspectives. The largest battleships with greater computation capabilities (i.e. Yamato, Nagato, Bismark) can have two, sometimes with distinct personalities from the other. Iona and Takao can also create [[FunSize miniature versions of themselves]] who have some measure of autonomy and can be used for shipboard tasks (or just be adorable).\\
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The actual Union Core that houses the Mental Model for each ship is actually quite small: Kirishima survives her destruction by throwing her own core to Haruna; Makie is able to pocket it later quite easily. Cores devoid of nanomaterials to interface with are completely helpless: Kirishima spent some time in Haruna and Makie's pockets; Haguro's core was swallowed by a shark until salvaged by Ashigara.

** Zuikaku quite regularly walks on the sea floor to get between her ship and the shore.