Arpeggio of Blue Steel

Plot

The world of the early 21st century was reshaped by climate change, as rising seas swallowed vast stretches of land. Then, in 2039, fleets of intelligent warships from the World War II era appeared, armed with strange, advanced technology. These vessels, known as the Fleet of Fog, crushed the world's navies and set up a total blockade of the seas and skies, cutting off all travel between nations. To improve their own tactical thinking, the Fog created Mental Models—human-like avatars housing a ship's Union core. These avatars developed distinct personalities as they learned to think more creatively than their ship forms. By 2056, seventeen years into the blockade, a former marine academy student named Gunzō Chihaya leads a privateer group called Blue Steel. They are notorious for commanding a Fog submarine, the I-401, whose Mental Model, Iona, has sided with humanity. Thanks to I-401's advanced tech and Gunzō's sharp tactics, Blue Steel has survived multiple Fog attacks and even destroyed one of their most formidable warships. A faction of the Japanese government hires Gunzō and his crew to transport a prototype vibration warhead to the United States, the only nation capable of mass-producing this weapon that might let humans fight back. The journey is fraught with dangers: the Fleet of Fog, human collaborators, and rival governments all have their own plans. Yet Blue Steel also finds unexpected allies on both sides, giving them a fighting chance against overwhelming odds.

Characters

Gunzō Chihaya is the main protagonist, captain of the I-401 and leader of the Blue Steel Fleet. He seeks not to destroy the Fleet of Fog but to achieve equal footing so negotiations for peace can be realized. Iona is the Mental Model of the submarine I-401 who left the Fog of her own volition to become Gunzō's vessel. Over the series, she develops human emotions, leading other Fog vessels to classify her as a traitor; those who come in contact with her either defect to the Fog, join Blue Steel, or experience errors in their mental models. After defeating Hyuga, the crew salvages and mounts the battleship's Super Gravitational Cannon onto the submarine's bow. In the manga, Iona uses M6A Seiran dive bombers, making her the only Fog vessel seen to utilize aircraft. In the Cadenza movie, it is revealed that the supreme flagship Yamato was defeated by her sister Musashi after a rampage, and Yamato's last wish was carried into Iona, giving her dual cores: to be Gunzō's vessel and negotiate with the Fleet of Fog to end the war—actions initiated by Gunzō's father. After defeating Musashi by becoming one with Yamato, Iona disappears, having served her purpose, and bids Gunzō farewell, but eventually returns. Sō Oribe is the first mate of I-401, always wearing a helmet supposedly due to allergies; he is Gunzō's closest friend and serves as helmsman and executive officer. Kyōhei Kashihara is the weapons officer, ranked 200th in his Naval Academy class unlike his friends who were in the top ten; he owns a large collection of gravure idol merchandise and often panics in crises. Iori Watanuki is the engineer operating the vessel's engines. Shizuka Hazumi is the sonar operator and a capable soldier who can take down several troops with skill and strategy alone; her past is mysterious, though she is known to have been to Taiwan.

Media

The manga first appeared in Shōnen Gahōsha’s Young King OURs magazine on September 30, 2009. Its first collected volume hit shelves on April 30, 2010, and by August 28, 2026, thirty-one volumes had been published. A guide book featuring a short story and a Drama CD also came out. Seven Seas Entertainment picked up the English license in July 2013, releasing the first volume on July 1, 2014; nineteen volumes had been issued by November 2021. A spin-off manga called Salty Road, drawn by TALI and following Takao, I-402, and Zuikaku as they sneak into Yokosuka, started its run in Young King OURs on October 16, 2014.

The CG anime adaptation, produced by Sanzigen under the title Arpeggio of Blue Steel -Ars Nova-, began broadcasting on October 7, 2013. Its opening theme is “Savior of Song” by Nano and MY FIRST STORY, while the two ending themes, “Blue Field” and “Innocent Blue,” were performed by the group Trident, made up of Mai Fuchigami, Manami Numakura, and Hibiku Yamamura. The TV series wraps up with an original ending that diverges from the manga’s storyline. When the show reran in 2014, it was paired with short comedy clips called Kiri-Kuma’s (Fog Bears), where the Fog characters appear as bears. In North America, Crunchyroll licensed the series, and Discotek Media handled distribution, releasing a Blu-ray/DVD combo pack on November 4, 2016.

In September 2013, a crossover with the online game Kantai Collection was announced. Illustrators from Kadokawa Games, including Shibafu and Konishi, created end cards featuring crossovers with Kantai Collection characters. A special in-game event for Kantai Collection ran from December 24, 2013, to January 6, 2014. Two animated films were announced in June 2014. The first, Arpeggio of Blue Steel -Ars Nova DC-, compiles the TV series with added scenes in its first half and a new story in its second half; Nano performed the theme song “Rock on.” The second film is an entirely new story. Both films were made by the same team as the anime and released in 2015. In 2017, scholar Takayoshi Yamamura observed that the anime was produced with cooperation from the JSDF Yokosuka District Headquarters and other JSDF units.