is a Japanese manga series produced by Ark Performance and serialized in Shōnen Gahosha's Young King OURs. 31 volumes have been released and an anime series by Sanzigen aired from October to December 2013. The same studio also produced two films based on the series, released in January and October 2015.
Plot Due to global warming and rising sea levels in the early 21st century, much of Earth's landmass has been lost. In 2039, fleets of powerful sentient WW2 era warships, armed with advanced technology and possibly 'alien' weaponry, mysteriously appear and devastate the world's naval forces. These ships, collectively known as 'The Fleet of Fog', impose a worldwide naval and aerial blockade, preventing humanity from both traveling the oceans and to other nations. During the blockade, the Fleet of Fog created Mental Models, humanoid avatars containing a ship's Union core, as a means to develop self cultivation and to overcome their lack of creative thinking of tactics that humans possessed, which at the same time made the Mental Models develop their own unique personality.
In 2056, 17 years after the blockade began, Gunzō Chihaya, a former student of the Japanese National Marine Academy, is the captain of a small group of privateers called the 'Blue Steel'. The Blue Steel are infamous for possessing a Fog submarine, the I-401, along with its Mental Model Iona, who defected to the human side. Due to I-401's technology and Gunzō's tactical skills, the Blue Steel have not only survived several encounters with the Fleet of Fog but managed to sink one of their most powerful warships.
Gunzō and his crew are hired by a faction of the Japanese government to deliver the prototype of the vibration warhead, a powerful weapon that may finally allow mankind to fight back against the Fog, to the United States. The United States is the only country with the resources and capability to mass-produce the weapon system. However, the Blue Steel will face obstacles on their journey not only from the Fleet of Fog and their human allies, but from other governments and factions with their own agendas. Along the way they will also gain allies of their own from both sides, increasing their chances against seemingly overwhelming odds.
Characters
Blue Steel Fleet
The main protagonist, captain of the I-401 and leader of the Blue Steel Fleet. He is not interested in destroying the Fleet of Fog, but to be on equal footing with them so negotiations leading to peace can be realized. I-401
The Mental Model (human avatar) of the submarine I-401 who left the Fog to become Gunzō's vessel of her own volition. Over the course of the series, Iona has developed human emotions which led the other Fog vessels to classify her as a traitor, but those who came in contact with her have either defected to the Fog, joined the Blue Steel fleet, or had the ship's mental model experience errors. After defeating Hyuga, the crew of the I-401 salvaged and mounted the battleship's Super Gravitational Cannon onto the bow of the submarine. In the manga, she has been shown to use the M6A Seiran dive bombers that her real life counterpart was equipped with, making her the only Fog vessel ever seen to utilize aircraft. In the Cadenza movie, it was revealed that the supreme flagship Yamato was defeated by her sister Musashi after she went on a rampage and had carried her last wish into Iona herself, therefore the reason for carrying dual cores inside her, which was to be Gunzō's vessel and negotiate with the Fleet of Fog to end the war, which was Gunzō's father's actions. After defeating Musashi by becoming one with Yamato, she disappears as she had served her purpose and bids Gunzō farewell, but eventually returns to him.
First Mate of I-401 who always wears a helmet supposedly due to allergies. He is Gunzō's closest friend and always knows what the latter is thinking. He wields the position as helmsman and executive-officer.
Weapons officer of I-401. Unlike the rest of his friends in the Blue Steel who were the top ten during their Naval Academy days, Kyōhei was in the 200th place. He also owns a huge collection of gravure idols merchandise and usually is the first to panic when the crew finds themselves in a pinch.
Engineer of I-401 who operates the engines of the vessel.
Sonar operator of I-401, she is also a capable soldier able to take down several troops with skill and strategy only. Her past is a mystery but it is known she's been to Taiwan.
A former Fog battleship and flagship of the Second Oriental Fleet who was defeated by Iona and her crew. Gunzō and the others salvaged her Super Gravitational Cannon and installed it on I-401. Hyūga's Mental Model (human avatar) has since become the port operator for the Blue Steel, with her ship's weapons and Wave Force Armor becoming the defenses for the island. She has been obsessed with Iona since their battle and views Iona's closeness to Gunzō as a hindrance to her affections, as well as Takao. Nevertheless, she cares for her companions' safety and assists with anything they need. She is also known to be a hacker, able to access the Fog vessels' systems and hack them in order to keep her vessels safe. In the Cadenza movie, she restores Takao's ship by consuming half of the Iwo Jima islands and travels with Takao to combat the Fog vessels of the student council in order to defeat Musashi.
The Mental Model (human avatar) of the Fog heavy cruiser Takao. After Gunzō defeats her in battle, Takao falls in love with him and later joins the Blue Steel fleet. She is almost destroyed for good by Zordan's fleet but is saved in the nick of time by a surprise attack from Iona and Hyūga. However, her core is salvaged by I-402 and delivered to Yamato, who assigns her to infiltrate a human facility in a special mission with the promise of being allowed to return to Gunzō's side once it is accomplished. The spin-off manga Salty Road follows Takao's days among other humans during said mission. In the Ars Nova adaptation, Takao sacrifices her vessel self to save Gunzō and the critically damaged I-401. This results in a super submarine called the Ars Nova with the processing capabilities and firepower of both Takao and Iona. She existed in a digital form inside the submarine's computer systems. At the end of the anime she regains her Mental Model form. In the Cadenza movie, she regains her ship after negotiating as a messenger to the Japanese government of the vibration warheads' codes with the help of Hyuga's skills and enters combat to save I-401 from the fog's student council and buys time in order for I-401 to defeat Musashi. She was originally equipped with a Super Gravitational Cannon, but her rebuilt ship instead used two large drills borrowed from the old base on Iwo Jima, much to Takao's annoyance.
Japanese government and military As a result of the blockade by the Fleet of Fog, both the Japanese government and Self-Defense Forces were reorganized. The government is led by the Prime Minister who deal with their own local affairs while making important decisions together for the entire nation. The JSDF became an actual military force with an Army, Navy and Air Force. The remnants of United States Forces Japan that were left stranded after the Fleet of Fog blockade were absorbed into the Japanese Military where many American servicemen ended up marrying Japanese nationals and starting families.
The Prime Minister of Japan. Kaede was Ryōkan Kita's former XO but was injured during the battle between the UN Naval Fleet and Fleet of Fog which left him in a wheelchair and the use of cybernetics to help him see and speak.
The Assistant Secretary of Military Affairs. He hires Gunzō and the Blue Steel Fleet to transport the Vibration Torpedo, the first human made weapon capable of destroying a Fleet of Fog ship, to the United States for mass production. He faces rivalry with Ryōkan Kita and his supporters who have their own plans for the I-401.
A former United States Marine Corps officer, now a Japanese Navy Lieutenant and Commander of United States Forces Japan. He is an ally of Kamikage in helping the Blue Steel fleet in their mission to transport the Vibration Torpedo to the United States.
An influential member of the National Diet expected to be the next Prime Minister of Japan and Ryūjirō Kamikage's rival. A former captain of a Japanese Navy Destroyer, he was a veteran of the last Naval battle between the UN Naval Fleet and the Fleet of Fog. Kita wants the I-401 returned to the Japanese government so they can reverse engineer it and make their own Fleet of Fog ships which puts him at odds with Kamikage. He has connections within the Japanese Army who hope to regain their prestige after the government chose to focus on the Japanese Navy.
Vice-Admiral of the Japanese Navy. He is Gunzō's ally since he knew his father and supports Kamikage's plans for the Blue Steel fleet.
Captain of Hakugei 3, Japan's newest attack submarine. Thanks to the help of the I-401, the Hakugei was able to defeat Kirishima and Haruna, becoming the first human vessel to defeat not one but two Fog ships. He and Ryūjirō are old friends.
A Japanese naval academy third year midshipman brevet ranked as an Ensign when detached at sea and the former sonar operator of the I-401. She was a classmate of Gunzō during their academy days and was in love with him and was the first to join his crew. However, unable to stand seeing Gunzō endangering himself, she left the I-401 and rejoined the Japanese Navy.
The Prime Minister of Japan and Mayor of Sapporo. He was created through genetic engineering just like Makie to be a better government administrator. Due to his body not having natural bacteria to digest food, he takes special medication to eat. Makoto claims to have no emotions but cares about his creator Tōjūrō Osakabe and his sister Makie. As a favor to his creator, he warns him that the Japanese Army is planning to eliminate him and Makie after Haruna's identity is discovered and sends a team of Cyborg Special Forces to extract Makie to Hokkaido.
Fleet of Fog/Japan This is the Fleet of Fog stationed in the Japanese territorial waters. They formed a blockade around Japan to prevent any human vessels and aircraft from fleeing to the open sea. There are 2 patrol fleets maintaining the blockade, the First and the Second Oriental Fleet. But when they found out that I-401 sinks Hyūga, the flagship of the Second Oriental Fleet, they are forced to reorganize, leaving a hole in the blockade. After they reorganize, Kongō is the new flagship of the Second Fleet while Nagato is the new flagship of the First Fleet.
The Supreme flagship of the Fleet of Fog and the one who gave the ability to the other ships to develop their own avatars. Yamato possesses two different avatars, one named after herself and another called Kotono. Both are modeled in appearance after the late Kotono Amaha, who was Gunzō's undefeated rival during his academy times and according to some of his friends, his love interest. It is uncertain if the Kotono Amaha that Gunzō knew was, in fact, human or Yamato's second avatar.