Aoki Hagane

Series logo as seen in anime

About the seriesEdit

Arpeggio of Blue Steel (蒼き鋼のアルペジオ Aoki Hagane no Arpeggio?) is a Japanese manga series produced by Ark Performance and serialized in Shōnen Gahosha's Young King Ours. Seven manga volumes have been released with an anime series developed by Studio Sanzigen in production (first episode is to be aired in October 2013).

General plotEdit

The series depict a slightly futuristic world of mid-21st century where humanity had lost much of the Earth's landmass due to the rising sea levels, caused by global warming. Almost as a response of Nature itself, mysterious battleships that look like reincarnations of WWII vessels start appearing all around the world, always surrounded by fog.

In year 2038, the ships of the so-called "Fleet of Fog" start to appear frequently, and in the very first battle between these battleships and human naval forces, a good portion of the Russian navy was annihilated. This battle had shown that the "Fleet of Fog" possesses weapons far beyond what humans had in their arsenal, and that the "Fog" battleships are surrounded by defensive shields that make any conventional weapons useless against them (While it is never discussed directly in the series, it is presumed that even nuclear weapons are useless or they are not effective enough to be considered as a countermeasure).

By the end of the year 2038, the "Fleet of Fog" began attacking human navies and soon had driven humanity entirely out of the seas. Since then, the "Fog" took a rather passive role and only maintained naval blockades, occasionally destroying some brave fools that tried to set sails in the open seas.


At the beginning, the story centers around Gunzou Chihaya, a former student of the Japanese National Maritime Institute of Technology, who is in possession of I-401 submarine, the only "Fog" vessel known to have defected to the humans' side, as well as Iona - the Mental Model and avatar of I-401 - and the rest of the small crew of the submarine.

As the series progress, other characters - both human and Mental Models of the "Fog" vessels - become additional focuses of the story.

The full list characters can be found here.

Plotline (manga)Edit

[Warning: contains spoilers]
Chapter by chapter retelling of manga events can be found here

During the first chapter, Gunzou Chihaya, Iona (the avatar of I-401) and the rest of the crew are seen completing random jobs. The latest one being protecting an SSTO launch site from a "Fog" light cruiser. Even though the launch was successful, SSTO was shot down over Hawaii, before it could reach its destination in USA.

Gunzou, being the only man who has even a chance at successfully crossing Pacific ocean, is contacted by Ryuujirou Kamikage, a representative of Japanese military, with a job to transport the last prototype of new vibration torpedo warhead to USA, where it could be produced en masse. After some internal debates, Gunzou and his crew decide they want to learn more about this job and so they set sails towards Yokosuka.

On their way there, they run into heavy cruiser Takao, a part of the "Fleet of Fog" blockade around Japan. Unable to escape the confrontation, I-401 is forced to fight an opponent with a superior firepower. The first clash resulted in I-401 losing her defenses almost completely, but in the second one, through the combination of surprise attack with a weapon I-401 wasn't supposed to have and some bluff, Gunzou managed to win. Takao, while not sunk, had her weapons temporarily locked down and was sent away, allowing I-401 a safe voyage towards Yokosuka.

In Yokosuka, Ryoukan Kita, current commander of JSDF tried to get I-401 from Gunzou and his crew-mates, however his attempt was interrupted when two "Fog" battleships - Haruna and Kirishima - attacked the port. Gunzou was allowed to remain in possession of I-401. Maybe an hour later, I-401 along with human submarine Hakugei (3) engaged and successfully sunk both battleships.

Mental Model of Haruna battleship, however, survived, as did Kirishima's core. They both were found by a civilian girl Makie - a Design Child who created the vibration warhead - when she came to the port following the battle in hopes of meeting her (fake and not existing) grandfather. Unaware of the true nature of the girl she had met, Makie invites Haruna to her home, where their friendship is formed. Some time later, the mansion where Makie lives is attacked by military. Haruna and Kirishima (currently inhabiting a body of a teddy bear) manage to push their way out of the besieged mansion, providing Makie with safe evacuation. Makie then is collected by special forces of Northern region. Just after that Haruna witnessed a death that caused her to go berserk and almost annihilate three nearby cities with the heavy cruiser Maya's weapons she had control over at that time. Before that could have happened, however, she was stopped by a new player (appears to be another Mental Model) in possession of legendary Admiralty Code. Once back to her senses, Haruna tries to fulfill her promise of remaining Makie's friend and is seen following her to the Northern region inboard of Maya.

Meanwhile, I-401 on its way towards Iwo Jima base is attacked by U-2501 submarine. The reincarnation of the German submarine managed to corner I-401, but the captain of U-boat, Zordan Stark, decided that it was not the time to sink them, thus allowing Gunzou's and Iona's adventures to continued.

Upon arriving to Iwo Jima, Gunzou finds out that heavy cruiser Takao is there as well. However, she herself had recently defected from the "Fleet of Fog" and is no longer antagonistic towards him. The same isn't exactly true about Takao and Iona, as the former now harbors a crush on Gunzou and sees later as an obstacle. Also, Mental Model of the Hyuuga battleship is introduced there. Hyuuga, once sunk by Iona, now manages the port and helps repairing I-401.

Later, Iwo Jima is attacked by JSDF, but I-401 (with Hyuuga inboard) and Takao manage to escape. To throw the pursuit off, Gunzou has Takao, who is a part of his fleet now, create a copies of crew members. Additionally, Takao is guiding a decoy I-401 to Yokosuka, while the real one is heading to rendezvous with Hakugei (3) - these two submarines would later deliver the vibration warhead blueprints and the last prototype to USA.

Shouzou Chihaya, Gunzou's father and the man-who-had-defected-to-"Fog" and the de facto commander of "Scarlet Fleet" faction of the "Fleet of Fog" makes his public appearance as he signs contract with the Queen of Great Britain. This causes the other battleships of the "Fog" reevaluate the current political climate in Western Europe.

Before Takao could complete her mission, she's attacked by U-2501 and her fleet of sea hound miniature submarines. Even though in the end Takao was sunk, the 'tsundere heavy cruiser' managed to make U-2501 reveal her trump card. The Mirror-ring system. Even though her Mental Model survived, Takao is not allowed to rejoin Gunzou - Yamato, the supreme flagship, stops being a mere observer and takes her prisoner: according to her, it's not the time for the I-401's crew to learn about this.

Just after Takao was sunk, I-401 sniped the resupply vessel Milchkuh, forcing U-2501 to retreat. As I-401 was on her way back to rendezvous with Hakugei (3), she was faced with the pursue fleet personally led by Kongou. Gunzou could see that I-401 on her own had little chances of getting past this obstacle, so he sneaked out with Hyuuga on a small shuttle submarine in order to have Hyuuga repossess her salvaged hull.

Meanwhile, Hakugei (3) became a witness of an infighting in the "Fleet of Fog". And after some thinking, captain Komaki decided to assist the running away battlecruiser Repulse by firing a Sound Cluster Torpedo and thus providing her with a sound screen that would allow her to shake of the pursuit. Later Repulse is seen contemplating, whether she should contact humans or whether she should keep her distance from them.

At the same time, Haruna finally manages to convince Makie to join her aboard of Maya and per the suggestion of the leader of the Northern Region Makoto Osakabe they are heading back to Yokosuka to try and learn what had happened during the Facility #4 incident.

While Gunzou and Hyuuga are away, I-401 is found by Ashigara and Nachi. The two heavy cruisers attack her, however, Iona manages to escape them. Myoukou, who was overseeing this encounter, decided that Ashigara should be recalled; her place as Nachi's partners was given to Haguro.

Two hours later (during these hours Iona's role as the heart of the Joint Tactical Network is revealed, however consciously Iona still doesn't know this), Iona decides that it is time for the "Blue steel" to counterattack. Using her active decoys loaded with Corrosive Warhead Torpedoes as a distraction, she tries to get close to Kongou. One of those decoys attacks Haguro and Nachi (and actually manages to sink the former), the other one attacks Myoukou and Hiei.

The real I-401 manages to get quite close to Kongou, but her attack on the First Oriental Fleet's flagship failed as Ashigara took the hit and Atago intervened, driving I-401 away. While I-401 was preparing for what was coming next, Kongou finished deploying her Flagship equipment.

Curious about what it was, yet unable to spy from a distance with the help of the drones, Iona decides to get close and take a look at this Flagship equipment. Hiei has anticipated this and made a strategy that resulted in Myoukou dealing serious damage to I-401's hull with her sniper cannon.

Meanwhile, Gunzou and Hyuuga have departed from Hakugei (3) and are now mounting a counterattack in hopes of protecting I-401 and (in the best case scenario) destroying Kongou and paralyzing her fleet for some time.

Plotline (anime)Edit

Anime begins with a brief history lesson about the "Fleet of Fog" and the Great Battle of 2039. Following that, the we are introduced to I-401 and her crew as they protect the SSTO launch site in Saga prefecture from light cruiser Nagara. The battle is quite similar to how it was made in manga, however, in anime I-401 goes all-out offensive right away, instead of trying to sneak up on Nagara first.

Following this battle, there is a flashback, showing how Gunzou came in possession of I-401: something that is not really shown in manga. Notable details about this flashback are the following: I-401 had a Mental Model fully-formed before she made contact with Gunzou; and there are no mentions of the Facility #4 fire or Kotono Amaha in anime. While it not clear, it also appears that Gunzou's mother, Saori, is dead in anime adaptation of the series.

The flashback is followed by the scene where Gunzou is in the meeting with Ryuujirou Kamikage, a representative of Japanese military. Kamikage reveals that the SSTO Gunzou has protected was delivering a Vibration Warhead Torpedo prototype to USA and was destroyed while in orbit. Then Gunzou is asked to do the delivery himself on I-401, something that he apparently agrees to do as he sets sails for Yokosuka.

On her way to Yokosuka, I-401 clashes with heavy cruiser Takao. This battle happens in the same way it does in manga and also results in the I-401's Super-Graviton Cannon collapsing and becoming unusable until it can be repaired with nanomaterials. Takao, deciding that she wants a captain of her own, runs away from the fleet (without a plan) and decided to switch sides. She is later (in episode 3) confronted by I-400 and I-402 about this.

Upon arriving to Yokosuka, Gunzou has another meeting with Kamikage. Unlike how it happens in manga, vice-admiral Uragami doesn't make an appearance, while Iona is accompanying Gunzou instead of remaining in the docks with her hull.

After the meeting with Kamikage, Gunzou and Iona visit the cemetery where Gunzou pays his respect to those who had died during the Great Battle (instead of bringing flowerst to Kotono's grave as he does in manga). Just before that, they also run across Makie Osakabe who was running away from her maids. It seems that unlike how the things were in manga, anime version of Makie has no hate towards Gunzou.

Like it happens in manga, all of the I-401's crew is collected by the army in order to bring them to Ryoukan Kita. In anime, however, Iona also comes as she was with Gunzou. Kita asks Gunzou to surrender I-401 to government,  but was answered with refusal. He tried to use force by summoning a group of armed soldiers, but the arrival of battleships Haruna and Kirishima prevented him from ...suppressing I-401's crew. At the end of the third episode I-401 is seen heading out to combat the battleships by herself.

I-401 dragged both battleships to the submerged part of Yokosuka, where she had prepared a minefield. And using the explosions of the mines, I-401 escaped Haruna's and Kirishima's sensors. With some of her nanomaterials placed on a husk of battleship Mikasa, I-401 managed to keep the battleships occupied until she could attack them from behind. That, however, didn't work, and I-401 was forced to escape the barrages of missiles Haruna and Kirishima unleashed.

It resulted in I-401 being buried under the rubble from the destroyed buildings and allowed the two battleships to catch her with a graviton pull of their combined Super-Graviton Cannon. Knowing that the Klein Field of the Wave-Force armor must be opened in order to fire the Super-Graviton Cannon, Gunzou tried to destroy both battleships with a single Corrosive Warhead Torpedo fired from I-401. That torpedo, however, was blocked. The second torpedo, fired from the semi-automatic launcher hidden in the shadow of Mikasa, however, successfully reached its intended target and blew both battleships up. As a result, Haruna lost her hull while Kirishima was stripped down to her core.

Following her victory in this battle, I-401 returned to the docks in order to get some much needed repairs as well as to have the Vibration Warhead Torpedo prototype brought inboard of it. While the said prototype was delivered to the docks, Gunzou observed Makie Osakabe ordering the men around as she instructed them on how to care for the torpedo prototype.

When Makie returns to the Osakabe mansion, she goes to her room, where to she brought 'unconscious' Haruna, whom she had discovered in one of the old warehouses. When Haruna awakens, she tries to pose herself as a human in order to avoid being ousted for what she is: a Mental Model. This leads to a bond of friendship forming between her and Makie. At that time, Haruna also allowed Kirishima's core to possess a body of a teddy bear.

However, her true nature was already known to the real master of the manor, Toujirou Osakabe, the creator of the Design Children and something like a father to Makie. (unlike how he was a butler in manga, in anime he is a bed-ridden and dying man who is holding onto his life in order to ensure Makie's happiness) Yet, despite knowing that Haruna was from the "Fleet of Fog", he still asked her to be Makie's friend. Soon after that he dies.

The government also knew about Haruna being a Mental Model and in order to nullify the threat of her kidnapping the Design Child and learning the secrets of the Vibration Warhead Torpedo, the attack on the manor in order to kill Makie was authorized.

Desiring to protect Makie, Haruna asked Kirishima to keep an eye on her while she confronted the military. Unfortunately, that didn't work out and Makie discovered Haruna's true nature; then she ran away in tears. Still desiring to protect the girl, Haruna created her dummy with nanomaterials and headed out to the mansion's backyard, drawing the military's attention to herself. Meanwhile Kirishima and Makie were to escape via the front gates. However, once the walking tanks, the "Stone crabs" were deployed, Haruna was forced to reabsorb the nanomaterials from the decoy, thus revealing that the real Makie was elsewhere.

A group of soldiers had discovered Makie a minute later, however, Kirishima in her bear form was able to knock them out before they could hurt the girl. And since Makie had resolved to still be Haruna's friend, she did something stupid and headed to where Haruna was still fighting against the military forces - Kirishima was unable to stop her. This all resulted in Haruna being forced to use all of her Wave-Force armor's strength to protect the girl with no chance of her to counterattacking. Knowing that sooner or later her defenses would be breached, Haruna cried out for help and, surprisingly, Iona showed up and forced the wounded military forces to finally retreat.

Instead of regrouping at Maya, Haruna and Kirishima (along with Makie) for some reason decided to join Iona inboard of I-401 as she sailed towards the Iwo Jima island.

"Fleet of Fog" learned that I-401 and the Vibration Warhead Torpedo prototype were at Iwo Jima. Kongou decided to attack and destroy them; her fleet consisted of herself, heavy cruiser Maya and six light cruisers. However, before the attack itself could begin, Kongou decided to answer Gunzou's request to come visit the island. She suspected that this was done as a form of mind games in order to make her change her mind about the attack. And, despite her doing her best to protect herself and Maya from it, those mind games did have some effect on her, making her obsessed with sinking I-401.

While Hyuuga, Kirishima and Haruna were powering up the shield around the island and distracting the Kongou's fleet, I-401 with just Gunzou inboard tried to slip away. However, she was noticed and Kongou tried her best to sink her, going as far as trying to activate her Super-Graviton Cannon while submerged and at point blank range. Hyuuga, however, managed to hack Kongou in time and redirected the attack away from I-401, allowing her escape using the burst mode.

Upon exiting the burst mode, however, I-401 was attacked by her sisters I-400 and I-402 and was hit by four Corrosive Warhead Torpedoes. The first pair was stopped by I-401's Wave-Force armor, but the later two were direct hits to the hull. This damage, while serious, wouldn't have been enough to end I-401 had I-400 and I-402 compromised her ability to repair herself as well. As the result, I-401 was left to sink towards her doom. Iona tried to do her best to keep Gunzou alive, but after sacrificing life-support systems, she ended up putting him in a suspended animation; she then placed him and her own Union Core in a coffin; though she still left a beacon in hopes that someone (Takao) will find them before it was too late.

Takao, indeed found them and, using Hyuuga's, 'egg' the tsundere heavy cruiser dove to the wreckage of I-401. Then Takao sacrificed her own hull in order to merge with I-401 and restore her.

In the aftermath of the battle between the "Blue steel" and Kongou's fleet, I-400 and I-402 suspended Kongou as the flagship of the First Oriental Fleet and temporarily took that role upon themselves. They also locked Kongou down, preventing her from going after I-401; they said that they will hunt her down themselves.

I-400 and I-402 find the restored I-401 and attack her. However, this time Iona was ready to fight back and with much help from Takao, Haruna, Kirishima and Hyuuga, she managed to overcome I-400 and I-402. And while she did sunk them both, Iona didn't want kill her sisters.

About the time I-401 sinks her sisters, Kongou manages to break the blocks and, after absorbing Maya and a number of light cruisers that were her fleet, she heads out to personally destroy I-401. By the time she catches up with I-401, American fleet was already there to intercept her. In her crazed state of mind, Kongou chose to annihilate that fleet - to eliminate any chance of those ships switching sides. Then she attacked I-401 herself.

To stop Kongou, who had cut herself from the Joint Tactical Network, it was decided that someone needed to establish a direct link with her. And Iona volunteered to do that. Meanwhile, the controls over her vessel were given to Takao and co. Iona was successfully delivered to Kongou's 'deck' and even managed to establish the link. However, Kongou had built a powerful defenses around her 'heart', so Iona needed a lot of time to break through. Even worse, while she was busy fighting against those defenses in the virtual world, she also needed to fight Kongou in the real world as well. And despite putting up a decent fight, Iona had almost lost - she managed to break through Kongou's firewall just moments before the two of them would have been swallowed by the Super-Graviton Cannon's shot.

Following her 'defeat', Kongou accepted Iona's friendship, but chose to return to her patrols around Japan instead of accompanying I-401 to San Diego.

Philosophical topics in manga/animeEdit

"Aoki Hagane no Arpeggio" series raise and try to answer several important philosophical questions:

  • What kinds of relationships between Humans and sentient Artificial Intelligence can be? It is shown throughout the series that AI of sufficient level can interact with humans much like another human would. The relationships possible vary from co-operational to antagonistic.
  • What can and cannot be called 'human' or 'humane'? Mental Models that spent some quality time around humans appear to become almost humans themselves. Iona, Yamato, and later Takao, Haruna and Hyuuga all act in the ways that make it practically impossible to distinguish them from humans through their behavior only. Many other Mental Models are also showing human-like tendencies, like having hobbies.
  • Artificial creation of life and playing God in laboratories, Is this allowed within human morale, and where to this can lead? This is still an open question even within the series: Makie and the leader of Northern region, Makoto, are two of the genetically-engineered for specific purpose humans. Makie had completed her mission already and thus her future depends on whether the politicians think she had earned her further life or not.

Anime trailer and openingEdit



『蒼き鋼のアルペジオ −アルス・ノヴァ−』PV第4弾!

『蒼き鋼のアルペジオ −アルス・ノヴァ−』PV第4弾!

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