Arpeggio of Blue Steel

Arpeggio of Blue Steel (Aoki Hagane no Arpeggio) is a fairly recent manga by Ark Performance, centering on humanity, having been pushed back from global warming raising the sea level, and their conflict with the Fleet of Fog, archaic-looking WWII-era ships who have been using Game Breaker weapons and armor to ensure that humans can't set keel or pontoon into the world's oceans without risking getting blown to smithereens. The world's navies banded together 17 years before the opening chapters of the manga and were utterly annihilated.

Since then, Japan's fortunes have gone downhill in a huge way: Japan relied on importing and exporting for both raw materials and income for its economy; without either, the nation's industry has fallen quite far. In this rather bleak future is one shining ray of hope: Blue Steel, a bunch of ragtag misfits led by their captain, one Gunzou Chihaya. Having somehow acquired a Fog ship of their own, the Fog submarine I-401, only Chihaya and his crew can actually claim Fleet of Fog kills in battle.

However, the I-401 and her crew have more enemies than just the Fleet of Fog: The Japanese government are very keen on getting their hands on what initially was their ship. Bureaucrats look at I-401 and drool. However, what nobody realized is that I-401, like many ships now in the Fleet of Fog, has a mind of her own, and a body to fit.

Tropes associated with Arpeggio of Blue Steel:

 * AI Is a Crapshoot: Somewhat inverted: Before getting 'Mental Models', the Fleet of Fog ships were pretty straightforward about their goals and how they went about achieving them. Now that they have them, however, they're finding that alongside having the point of view of humans, they're also starting to pick up quirks like humans too...
 * Alternate History: The manga takes place in a setting where Russia masters supercavitation technology in the 1990s, and supercavitation torpedoes are invented. These torpedoes essentially make modern navies obsolete, and then the Fleet of Fog showed up.
 * In the real world, the VA-11 Shkval has already been in service since the late 1990s with the Soviet, and later Russian Navy. However, current supercavitation torpedoes like the Shkval have to slow down in order to maneuver or use their guidance systems, negating their primary speed advantage.
 * Aluminium Christmas Trees: 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.
 * Anthropomorphic Personification: Fleet of Fog ships of heavy cruiser class and up (including large submarines) all have one. Iona is shown having at least 9 moving around. They represent the 'Union Core', which may or may not be the AI that runs the ship in question.
 * The Union Core is confirmed to be the AI that runs the ship; when Kirishima is destroyed, Haruna manages to save her core. Later chapters show Kirishima is still active, but cannot communicate with Haruna beyond the joint tactical network.
 * Applied Phlebotinum: The Fog Fleet is made of nanomaterial.
 * Beehive Barrier: The 'Klein Field' shielding used by the Fleet of Fog tends to take this form when blocking fire. Oddly enough a similar effect is seen when using the Wave Motion Gun on the I-401.
 * Beneath the Mask: Lawrence acts the titular Battle Butler, but he is actually
 * Big Damn Heroes: The first chapter opens with one of these, having Iona atop the I-401 rising up from the water and crushing a concrete pier to save her captain and his charge, terrify the living daylights out of some gangsters, and cause some property damage to boot!
 * Black Box: Most of the Fleet of Fog technology is described as this. Even though they had I-401 in their possession, neither the Japanese government nor its crew actually know how its specific components work. One example is the Corrosive Torpedo, which they have a very limited amount of and have no means of reproducing.
 * Cannot Spit It Out: In Chapter 21, after much preparation, Takao confronts Gunzou, intending to ask him to become her captain... and instead demands the vibration warhead and data.
 * Child Prodigy: Makie Osakabe, who designed the vibration torpedo.
 * Creepy Child: Iona has occasional shades of this.  And completely averted with Takao's mini versions, who are moe incarnate.
 * Coat Cape: Haruna wears a heavy one covering her all up to nose
 * Combining Mecha: Fleet of Fog warships are capable of doing this. Takao linked up with I-501 in order to improve her anti-submarine capability, while Kirishima and Haruma combined both of their Wave Motion Guns into a single massive Wave Motion Gun.
 * Cool Ship: This manga is an ode to cool ships of the IJN.
 * Cool Mask: First Mate Sou has two; the first allows him to interface directly to 401's systems, likely equipped with a Heads-Up Display. He has a second, smaller one to use when maintaining the first.
 * Crapsack World: The current situation is strangling Japan to death economically (see Easy Logistics), and Europe is said to be in the midst of a civil war.
 * Defeat Equals Friendship: More like Defeat equals crush - Hyuga defects to Gunzou's force after being defeated, due to her fixation on Iona-sama.
 * Takao looks likely to become this as well, on top of her Stalker with a Crush attitude towards.
 * Did You Just Punch Out Cthulhu?: The Hakugei III
 * Easy Logistics: Subverted. The Fleet of Fog's interdiction of sea and air transport routes is adversely effecting Japan's economy, being an island nation reliant on trade (a repeat of what happened in WW 2). Other nations are also stated to be affected; the one nation that seems to be doing alright despite the Fog is the United States, as it's one of the few nations that are completely self-sufficient.
 * Game Breaker: 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 Supercavitation technology for torpedoes. This made torpedoes capable of going more than 300 knots the standard of naval warfare. 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 VA-11 Shkval, vs 38km for the ADCAP.
 * Humans Are Special mixed with Bastards:  is keenly aware the only reason the Fleet of Fog is dominating the world's oceans is because of their Game Breaker Wave Motion Gun, and the moment humanity catches up, which will eventually happen, human tactics and strategy with equal weapons will mean the Fleet of Fog is screwed.
 * Interservice Rivalry: Due to the nature of the conflict with the Fleet of Fog, the Japanese Army has largely been ignored in favor of the Navy, much to their chagrin. This is the primary motivating factor why they've aligned with Kita, since they're desperate to win some recognition.
 * Kaiju Defense Force: Gunzou Chihaya was originally an officer cadet, and his father was a JMSDF Commander, who was the first captain of I-401 after she was captured by the Japanese Navy.
 * The JMSDF appears in several instances, being mostly helpful to I-401's crew - it helps that the CNO was a friend of Souzou Chihaya. The prototype submarine Hakugei assists in I-401's takedown of Kirishima and Haruna.
 * Katanas of the Rising Sun: So far, all ships seen in the Fleet of Fog's Far East Fleet are Imperial Japanese Navy vessels.
 * Nazis With Gnarly Weapons: It's mentioned that one of the flagships of the European based fleets is the Bismarck. Also, U-2501 appears, commanded by Zordan Stark,.
 * Laser Sight: 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.
 * Macross Missile Massacre: One of the tactics used by Takao, who puts up an impressive volume of fire for a mere heavy cruiser. She's later on the receiving end when approaching Iwo Jima.
 * Mugging the Monster: A Mental Model without her battleship. What could possibly go wrong?
 * Noodle Incident: Everybody talks about how the I-401 and its crew sunk the Hyuuga, but we've never actually seen the battle nor have we been given an accurate summary of events.
 * Orcus on His Throne: 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.
 * Oh Crap: Lawrence, Makie's butler, has this reaction.
 * The Ojou: Yamato gives off this vibe, what with being a Yamato Nadeshiko.
 * Phlebotinum Analogy: The explanation of how the Klein Field works.
 * Pretty in Mink: Musashi, in her guise as a Russian Snow Girl.
 * Reality Is Unrealistic: One of the more common human weapons is a rocket-propelled torpedo. Such weapons have been in service since 1998.
 * Hakugei uses a rocket engine to achieve supercavitation. This is currently under research by DARPA.
 * Reasonable Authority Figure: 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.
 * Right Hand Versus Left Hand: 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.
 * Robot Maid: Several run the Osakabe mansion and are realistic enough that they aren't revealed as such for several chapters.
 * Scenery Porn: Ark Performance shows what drawing Gundam manga for years does for skill at drawing mecha and landscapes. The 2400p versions of the scanlated manga are recommended to see just how much detail they put into everything.
 * Screw the Rules, I Have Money: Invoked by Makie when a cab driver attempts to protest the apparent little girl trying to catch his cab by herself. His reaction to her SPECIAL GOLD CASH CARD is priceless.
 * Shout-Out: All of the Fleet of Fog ships are replicas of real life WWII era warships.
 * Show Within a Show: Hisonic Miku-chan, an anime popular with Makie Osakabe, Kyouhei and Iona (A Is like anime, too).
 * Spaceship Girl
 * Stalker with a Crush: Takao is pretty quickly turning into this for.
 * Transforming Mecha: The Fog Fleet ships are all replicas of WWII warships only on the outside--.
 * The Reveal: mental models are the splitting image of
 * Unobtainium: Thanatonium.
 * Villainous Breakdown:
 * Takao suffers this after getting defeated by Gunzou, but compensates by.
 * Haruna has one after she learns the concept of death.
 * Wave Motion Gun: While the Fleet of Fog on the whole has dramatically superior armaments and shielding to the human fleets, Battleship-class vessels come equipped with 'Super Heavy Cannons', which despite the name fill the trope nicely, since the weapon tends to bend space around it and it's firing path.
 * We Can Rule Together: After cornering the 401 and its crew, Zordan suggests Chihaya to join the Fleet of Fog under his boss,
 * What Measure Is a Non-Human?: When Gunzou realizes that some of the Fleet of Fog ships are self aware like Iona, he decides to spare Takao rather than kill her.
 * Yanks With Tanks: The US Pacific Forces who were stranded in Japan; as Fleet of Fog interdiction of air and sea routes makes returning them to the US impossible, they've been absorbed into the JMSDF as the Unified Forces.
 * You Are Number Six: I-401 is the ship's initial designation, though her mental model is called Iona by the/her crew.