| Portrait | Mental Model | Vessel | Ars Nova|
Super-Graviton cannon | Joint Tactical Network Avatar
Mental Model information:
|Affiliation||Blue Steel, Chihaya Gunzou (current), Fleet of Fog (former)|
Mental Model's Appearance:
|Hair color||Light Blue|
|Status|| Active (manga);|
Sunk and restored (anime)
|Sunk by||I-400 and I-402 (anime)|
|Type||"Fleet of Fog" Sen-toku class submarine|
|Maximal Speed|| 80 knots submerged|
60 knots surfaced
|Armament|| 8x Torpedo tubes;|
11x Photon cannons;
18x Missile launchers;
3x Seiran Bomber Drone
I-401 is a reincarnation of a Sen-toku class WWII Japanese submarine, upgraded with "Fog" technology. Originally I-401, like her two 'sisters' I-400 and I-402, was a surveillance submarine within the "Fleet of Fog"; but she was later re-equipped as an attack submarine. She has therefore lost most of her surveillance equipment other than the basic sensors equipped in regular ships in exchange for more offensive weaponry.
Armament and defensesEdit
I-401 has 8 front torpedo tubes, several Photon cannon turrets for active anti-torpedo and anti-missile defense systems, and an unspecified number of rear torpedo tubes. Ammunition for the torpedo tubes includes but is not limited to: Corrosive Warhead Torpedoes, Anti-Masker torpedoes, Active Decoys, Passive Decoys, and Anti-Sub missiles. Additionally, after sinking battleship Hyuuga I-401 was equipped with a salvaged Super-Graviton Cannon. Later, this cannon was further improved via two support vessels, auxiliary Super-Graviton Cannon ships SGCS-01 Itsukushima and SGCS-02 Hashidate.
As of chapter 72, I-401 can use attack planes (WWII style ones) to deliver Corrosive Warheads to the desired targets. This makes her the only "Fleet of Fog" vessel to utilize aircrafts offensively after the Great Battle of 2039.
I-401 has a moderately-powerful Wave-Force armor that can protect the hull from a single grazing hit from a Super-Graviton Cannon or two direct hits from Corrosive Warhead Torpedoes. Without this armor I-401 is not much sturdier than a conventional submarine; however she's much faster than any human submarine, save for Hakugei (3) while in super-gavitation mode, and is capable of reaching 80 knots while fully submerged. More if she focuses entirely on speeding to her chosen destination.
While I-401 is a "Fog" vessel, she has perfectly working facilities that an AI-operated machine doesn't need: a bridge, a wardroom and personal cabins for the crew. It's not clear whether those were present there originally; but is unlikely that they were installed by humans before I-401 was sent on her first manned voyage with Shouzou Chihaya as her captain, as human technologies are not enough for such redesign.
BridgeEditI-401's bridge room appears to be a roughly spherical room with light-gray walls, though normally the lighting is toned down and they appear to be much darker. Just in front of the entrance hatch there is a raised platform with the seats for the first mate (right) and the captain (left). Between these two seats there is an elevation on which Iona is often sitting. In front of this platform, there are three crew stations arranged in a semi-circle. Out of those three, the central one (Fire Control) is occupied by Kyouhei and the left one (Sonar) by Shizuka. Above the central station there are big screens that are used to display tactical data. During the first "voyage" I-401 had with Gunzou, no other consoles were present other than the raised platform, the captains seat, and the main tactical display. It would appear that I-401 is capable of reconfiguring itself using nanomaterial.
Engine RoomEditI-401's engine room looks completely unlike anything that can be found on any human-made submarine, even one as advanced as Hakugei (3). This is something to be expected, though, as I-401 was and still is a "Fog" vessel. From what little is known about the technology of the "Fleet of Fog", I-401 is using Thanatonium as its power source; and as such, her engine room is actually a reactor room where energy is harvested from Thanatonium's decomposition into graviton particles. This energy is then transferred to all inboard facilities through superconductive cables.
IonaEditIona is the Mental Model of the I-401 submarine. She's one of the oldest Mental Models in existence and, having spent around two years with humans, she is one of the most versed in the human way of life. Unless she reveals her abilities, it is practically impossible to distinguish her from a normal human.
Iona appears as a girl in her late pre-teens with long white with blue tint hair, pale skin and green eyes. Her clothes vary, especially in the manga. In the anime only two sets of clothes for her have been confirmed. When appearing in swimwear, Iona is always seen in a one-piece swimsuit.
Iona is usually calm and rather quiet; she's helpful towards her crew and is a dear friend of Gunzou. She doesn't like taking big risks, but often agrees that Gunzou's sometimes rather crazy plans are the best ones. Iona appears to be sharing various duties like cleaning and cooking with her crew. It doesn't look like she has any definite hobbies, but she likes watching anime.
The true reason why I-401 and Iona as her avatar allies herself with humans is still unknown, but her alliance with Gunzou looks to be genuine. At one point supreme flagship Yamato says that Iona is allying herself with Gunzou completely out of her own free will.
Joint Tactical NetworkEditIn Chapter 53 it is revealed that Iona literally is the Joint Tactical Network. For this reason, she can't be cut off from it no matter what. However, Iona doesn't consciously know about this role of hers.
While actively participating in her capacity of being the Joint Tactical Network, Iona's appearance changes somewhat. Her hair turns darker, probably becoming light-brown; in addition, her clothes change to Yamato-style dress, which bears insignia of the "Fleet of Fog" on it. Interestingly enough, the dress has I-401's insignia as well, and it is always there on Iona's forehead when she is in the information-scape of the Joint Tactical Network.
- I-401 and Iona both appear in the first chapter of the manga. At that point, she had already been allied with Gunzou for about two years. In flashbacks it is shown that Iona had infiltrated the Japanese National Maritime Institute and sought out Gunzou. When he later came across the I-401 submarine, Iona re-materialized as a part of her vessel.
- In the anime, I-401 already has a Mental Model when she meets Gunzou. She actually infiltrates the Japanese Maritime Institute of Technology as Iona and lures Gunzou to the harbor, where she reveals herself as a Mental Model to him. After their alliance is formed, I-401 breaks free from the dry-docks where she was locked up and comes to collect Gunzou and Iona. Then they disappear into the sea after eluding pursuit.
Role : MangaEdit
I-401 has quite a long history, which starts nearly at the same time as when the "Fleet of Fog" started to actively attack human fleets. However, the most eventful times for I-401 are the recent years when she has Gunzou Chihaya as her captain.
Early days: 2039-2046Edit
As the "Fleet of Fog" possessed both firepower and defenses light-years ahead of what humanity could produce with its current technology and scientific knowledge, the "Fog" warships easily overwhelmed any single fleet that dared to oppose them. In a desperate attempt to let humankind back into the seas, a great united fleet was formed in 2039. It was defeated and seventy percent of it was destroyed. The only small victory of that time was the successful capture of I-401 by JMSDF Commander Shouzou Chihaya through means unknown. I-401 was brought to Yokosuka port in order to be studied.Any and all attempts to even understand the technology involved in her creation, however, failed; and after six years, the Japanese government finally gave up and decided that I-401 would be used to combat "Fleet of Fog" as she was. Shouzou Chihaya was appointed as her captain and sometime in 2045 I-401 was sent on her maiden (manned) voyage, despite the opposition's protests.
Contact with I-401 was lost while it was somewhere in the middle of the Pacific Ocean. To this day it is unknown what happened there; however, at that time it was assumed that she went MIA with her crew dead. After almost a year, I-401 surprisingly returned to Yokosuka without her crew. She was placed into a dry-dock and locked up.
Formation of I-401's crew: 2054-2055EditSometime in year 2054 (after the fire in Facility #4), I-401 broke free from the dry-dock where she was kept. She met Gunzou Chihaya and together they escaped from the port of Yokosuka. For some time it was just two of them; then Maruri Hibiki - the original sonar operator - joined them. After that, Iori Watanuki (in charge of the engines), Kyouhei Kashihara (in charge of weapons) and Sou Oribe (I-401's first mate) joined.
About a year after the escape from Yokosuka, I-401 had her first serious fight. She managed to sink the Fog battleship Hyuuga, who then proclaimed Iona as her Goddess of War and joined them. Gunzou left Hyuuga in charge of his base at Iwo Jima, while I-401 continued her adventures.
Following the fight with battleship Hyuuga, Maruri left the crew temporarily leaving I-401 without a proper sonar operator. Then about eight months before the series start, Shizuka Hodzumi joined the crew and became their new sonar operator. Out of the six humans that ever made up the crew of I-401 under Gunzou's command, Shizuka is the only one who didn't attend Japanese National Maritime Institute of Technology. Right now, her reasons for joining the crew are not clear.
Current days: 2055-2056Edit
During the first chapter Iona is seen assisting Gunzou with random jobs; the latest one being protecting an SSTO launch site from a "Fog" light cruiser. After that is done, Gunzou is contacted by Ryuujirou Kamikage, a representative of Japanese military, with a job to transport the last prototype of the new Vibration Warhead Torpedo to the USA. I-401 sets sail to Yokosuka to pick it up.
On her way there she runs into heavy cruiser Takao, a part of the "Fleet of Fog"'s blockade around Japan. Unable to escape the confrontation, I-401 is forced to fight an opponent with a superior firepower. The first clash results in I-401 losing her defenses almost completely; but the second one, through the combination of surprise attack with a weapon I-401 wasn't supposed to have and some bluffing by Gunzou, she managed to win.
In Yokosuka, I-401 remains in the dry-docks until two "Fog" battleships - Haruna and Kirishima - attack the port. She then escapes the docks (again) and with some help from Hakugei (3) collects Gunzou and the rest of the crew. From this point on, I-401 starts her own fight against Haruna and Kirishima; however those two have even more firepower than Takao and I-401 is severely outclassed. In the end, Gunzou comes up with a daring plan that uses I-401 as bait. The plan works and Hakugei (3) is able to destroy both battleships with a singe corrosive torpedo (given to them by Iona). After the battle ends, I-401 heads to the Iwo Jima base for repairs and to restock her ammunition.
On her way towards Iwo Jima Iona is attacked by the submarine U-2501. The reincarnation of the German submarine manages to corner I-401 and forces her to surface. Mysteriously the captain of the U-boat, Zordan Stark, decides that it is not the time to sink them and lets them go; thus allowing Gunzou's and Iona's adventures to continue.
When Iwo Jima is attacked by Japanese Special Forces, I-401 leaves an active decoy for them to capture while she herself (with Hyuuga aboard) and Takao escape. From there I-401 heads to a rendezvous point with Hakugei (3), which is supposed have the documentation and the last prototype of the Vibration Warhead Torpedo they are supposed to bring to the USA.
Just after Takao is sunk in her confrontation with U-2501, I-401 snipes the resupply vessel Milchkuh forcing U-2501 to retreat. Then I-401 searches for Takao's core until I-402 posts on the quantum network that she has it. Upon receiving this message, I-401 withdraws from those waters and rendezvouses with Hakugei (3).
On their way to the rendezvous point, I-401 comes in contact with Kongou's pursuit fleet which consists of Kongou herself, battleship Hiei, and heavy cruisers Atago, Myoukou, Haguro, Ashigara and Nachi as well as a number of lesser vessels. At this point, it is decided that Gunzou and Hyuuga will slip through the blockade in a miniature submarine (Matsushima), recover Hyuuga's hull and return to assist I-401 out of the blockade.
However, heavy cruisers Ashigara and Nachi find I-401 before that plan can reach its completion and I-401 (under Iona's command) is forced into battle. Iona chooses to do her best at making the heavy cruisers lose her, and she seems to be rather successful with this at the time. She also manages to land a serious hit on Ashigara forcing her to temporarily retreat to the surface.
While she is hiding following that action, Iona goes into hibernation for two hours as she prepares for a counterattack against Kongou's fleet. During this time she finds herself in a virtual space, where her additional role as the manager of the Joint Tactical Network is revealed to her. However, she is forced to forget about that role before she is allowed to 'wake up'.
Iona's plan for the counterattack is the following: two of her active decoys loaded with Corrosive Warhead Torpedoes are to attack Haguro and Nachi and Myoukou and Hiei respectively (in order to confuse those vessels, Iona would control the decoys directly while her crew would control the main vessel). This tactic, while deciphered by Hiei rather quickly, was still quite successful. More than that, one of the decoys managed to actually sink heavy cruiser Haguro.
Once Kongou had her Flagship equipment deployed, Iona decided that collecting data on it was in order. However, since the thing created some huge spatial distortions that made the usage of reconnaissance drones impossible, Iona needed to come close and observe in person. Her curiosity was predicated by Hiei and used against her.
While I-401 managed to take the photos of Kongou's Flagship equipment without much problem, she was almost immediately afterwards sniped by Myoukou, taking some serious though not yet critical damage to the hull.
Among other things, this left Iori stranded in the engine compartment without any available way to join the rest of the crew in the living quarters. This, coupled with the leakage of some presumably-poisonous gas created the first very real threat to the life of Iona's crewmate. Situation is only made worse by the fact that "Fleet of Fog" doesn't seem to be generous enough to give Iona the time she needs to properly fix the damage she has sustained so far.
Iori was saved by Ashigara and Haguro who ended up inside I-401's hull. The Mental Models of the two heavy cruisers then agree to assist Iona in surviving the current battle as they would be destroyed alongside with her.
Having assigned Ashigara to assist Kyouhei and Haguro to Sou, Iona and Gunzou focus on their next move. Which is to distract the Kongou's fleet with taking away their buoyancy by blowing up an underwater deposit of Methane Hydrates. And then, while they are unable to dodge, shoot them.
The first part of this plan actually goes pretty well - even if Yukikaze had to add a number of her own munitions to make it work as Gunzou wanted. During the second part, Iona sends three warplanes she controls directly to attack Kongou and actually manages to land a serious hit on the fast battleship.
Role : AnimeEdit
The beginning (2054 - 2055)Edit
In anime, little is known about what was happening to I-401 prior to the warehouse 51 incident when Chihaya Gunzou touched her hull, forcing her awakening. It's made to look like she had came to Yokosuka port with her weapons locked on her several years before that accident; according to her own words, Gunzou is the first human inboard of her, which means that unlike how it was manga, Shouzou never was her captain.
Upon her re-activation, I-401's Mental Model assumed an appearance of the Japanese Maritime Institute of Technology student and infiltrated the establishment in order to contact Gunzou and possibly get him to become her captain. Despite his orriginal doubts, Gunzou ended up agreeing to make her his ship and the two of them escaped Yokosuka.
Battles with Nagara and TakaoEdit
The chronologically next time she appears, I-401 already has her crew "full" with, Iori Watanuki in charge of engine, Kyouhei Kashihara in charge of weapons and Sou Oribe being first mate. Her sonar operator is Shizuka Hodzumi.I-401's first shown mission was protecting an SSTO launch site in Saga prefecture from the attacks from the "Fleet of Fog" light cruiser Nagara. This mission was successful with Nagara being sunk, however, the SSTO was later destroyed while in orbit - Gunzou learnt this from Kamikage Ryuujirou, and was next asked to deliver the last existing prototype of the Vibration Warhead Torpedo to USA.
That didn't really work as heavy cruiser Takao was assisted by the surveilance submarine I-501, who was capable of detecting I-401 from a great distance despite the storm. Unable to slip by the pair and not willing to take the risk of bringing a "Fleet of Fog" to port Yokosuka, Gunzou had I-401 engage Takao in combat. The first attempt was a failure as Takao almost sniped I-401 with her Super-Graviton Cannon, but then I-401 revealed her own one and destroyed I-501, and with some bluff Gunzou made Takao surrender.
Upon her arrival to Yokosuka port, I-401 was restocked with provision and conventional ammunition; some repairs were also made, though without restocking on nanomaterials at Iwo Jima, I-401's Super-Graviton Cannon, that collapsed during the battle with Takao, could not be repaired. While her hull was being repaired, Iona accompanied Gunzou to his meeting with Kamikage Ryuujirou and, later, to cemetery, where they were confronted by Ryoukan Kita's men.Not willing to fight in such a place, Gunzou agreed to come with them and was delivered to a restaurant where Ryoukan Kita and the rest of the I-401's crew were waiting for them. Ryoukan Kita then asked Gunzou to surrender I-401 to the government. Gunzou refused and Ryoukan Kita was ready to use force to achieve his goal, when battleships Haruna and Kirishima arrived.
Upon Gunzou's orders, I-401 engaged them. In attempt to minimize to possible damage to the port itself, the battleships were dragged to the sunken part of the Yokosuka city, where I-401 utilized her stealth capabilities and local complex underwater currents to maximize her chances of survival and victory.
While Gunzou's original plan to sink Kirishima by attacking her form behind while she was concentrated on a decoy made from the battleship Mikasa's husk didn work, the said husk was used to hide a launcher that eventually fired a Corrosive Warhead Torpedo that destroyed both battleships Haruna and Kirishima while they were united in order to use their overpowered Super-Graviton Cannon.
Following this battle, I-401 returned to Yokosuka port docks, where the Vibration Warhead Torpedo was finally loaded onto her. As they were departing from the citadel port, I-401 heard Haruna's prayer for help and came to investigate. After confirming that the battleship's Mental Model's desire was only to protect Makie Osakabe, she assisted them by forcing the army troops to retreat. Following that, Haruna, Makie and Kirishima were welcomed aboard of I-401 as guests (the Mental Models had their abilities restricted, though).
Iwo Jima and beyondEditUpon arriving to the base at Iwo Jima, it was discovered that heavy cruiser Takao was already waiting for them there; however she was not seeing them as enemies to be destroyed anymore. Right now Takao's goal was to make Gunzou her own captain.
Some conflicts among the five Mental Models on the base - and there were some without a doubt - however did little to prevent everyone from getting the well-needed rest and, in I-401's case, repairs as well.
The peaceful time, however, didn't last long as soon "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, beforethe 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 portect 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 compromissed 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 sacrifising 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 wreakage of I-401. Then Takao sacrifised her own hull in order to merge with I-401 and restore her.
I-400 and I-402 learn about that and after suspending Kongou from her position of the First Oriental Fleet's flagship, went out to hunt the restored I-401 down. 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 sink them both, Iona didn't want to 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 aready 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.
Since Kongou had cut herself from the Joint Tactical Network, in order to contact her, someone needed to establish a direct link with her core. In other words, someone needed to come all the way up to Kongou's 'deck' and touch her Mental Model. Iona volunteered to do that.
Iona had been successfully delivered to Kongou's 'deck' and actually managed to tag her core, however, Kongou had built a powerful defenses around her 'heart', so Iona needed a lot of time to break through. And while she was fighting against those defenses, Iona also had to fight against Kongou's Mental Model in the real world. This fight was one-sided and Kongou totally dominated it. In the end, she managed to pin Iona against the Super-Graviton Cannon and prepared to fire.That was when Iona finally managed to break through the defenses around Kongou's core in the virtual world. Once able to come in contact with Kongou's self, Iona, wishing to help her, proceeded to comfort the crying battleship. And accepting this, Kongou ceased her attacks in the real world.
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.
Ships sunk by I-401 Edit
During the captaincy of Chihaya Gunzou I-401 has sunk a number of the "Fleet of Fog" vessels:
- Ise-Class Battleship Carrier Hyuuga
- Nagara Class Light Cruiser Nagara.
- I-501, type IXD2 U-boat Surveillance Submarine.
- (anime only) Kongou-class Fast Battleships Haruna and Kirishima.
- (anime only) Sen-toku class Surveillance Submarines I-400 and I-402.
- (manga only) Type XIV U-Boat Resupply Vessel Milchkuh.
- (manga only) Myoukou-class Heavy Cruiser Haguro.
- (manga only) Myoukou-class Heavy Cruiser Ashigara.
- (manga only) Myoukou-class Heavy Cruiser Nachi.
In Addition to these vessels, after she had escaped from Yokosuka with Gunzou Chihaya inboard, but before her battle with battleship Hyuuga, I-401 has also sunk at least one "Fleet of Fog" destroyer and one submarine; and at least two light cruisers were confirmed to have been sunk by I-401 near Bounomisaki, where the hull of Hyuuga lies.
Finally, Iona manages to cripple Kongou during their latest encounter.
- Gunzou Chihaya - Her captain and dear friend. She allows him a lot of things and follows his often crazy plans without any real complaints. He returns her feelings of friendship in kind. Moreover, when asked to surrender I-401, Gunzou states that Iona is his crewmate and he will never sell her, no matter what.
- Iori Watanuki - Iona's second-closest friend. Iori manages I-401's engine and energy systems, and as such Iona has spent a lot of time explaining various technical details to her.
- Kyouhei Kahihara - Iona's fellow anime fan. Additionally, he's the man in charge of I-401's weapons.
- Hyuuga - Current co-processor for Iona. Hyuuga, once defeated by I-401 and her crew, abandoned "Fleet of Fog" and alligned herself with them. She sees Iona as the Goddess of war and practically worships her. And lusts after her as well, which often annoys Iona. Hyuuga also does repair or upgrade I-401's equipment that is beyond humans' understanding.
- Takao - Originally an enemy, Takao later becomes a part of Gunzou's "Blue Steel", and as such Iona treats her as an ally. Takao, on the other hand, sees Iona as a rival for Gunzou's heart and is slightly antagonistic towards her.
- Shouzou Chihaya - Their meeting happened before I-401 got her Mental Model. Shouzou and several of his men had boarded I-401 some years before the series start, before disappearing from Japan.
In general, Iona shows an incredible amount of trust in her current crew, going as far as to give them full control over her boat while she performs other actions that require her full attention (e.g. guiding decoys or warplanes).
- I-401 is the only known vessel in the "Fleet of Fog" that has a single Mental Model, with a name that differs from the name of the vessel itself.
- Iona is the first Mental Model seen in the series. I-401 is the first "Fog" vessel seen in manga.
- Iona can create her (lesser) copies so that she can help in different places simultaneously. These copies have numbers on their foreheads and are usually seen somewhere around Iori. The only other "Fog" vessel to show this ability is Takao.
- I-401 is the only known "Fleet of Fog" vessel that had two human captains.
- According to anime, I-401 was stored in warehouse 51. Considering that she's something that could not be studied by human scientists, this might be reference to the infamous Area 51.
- In the anime, while I-401 is under Gunzou's command, her deckhouse has an inscription: "Dreifach ist der Schritt der Zeit: Zoegernd kommt die Zukunft hergezogen Pfeilschnell ist der Jetzt entflogen Ewig still steht die Vergangenheit.." (A quote from Friedrich Schiller: Threefold the stride of Time, from first to last:
Loitering slow, the Future creepeth--
Arrow-swift, the Present sweepeth--
And motionless forever stands the Past.)
- Iona is voiced by Aoi Yūki in Drama CD and by Mai Fuchigami in Anime.
- Being a Sen-toku class submarine, I-401 (the WWII one) was one of the biggest diesel submarines ever built. Submarines of this class are biggest submarines of the WWII.
- In the end-of-episode guest illustration of episode 1 of the anime, I-401 is depicted with another I-401 from the Kantai Collection browser-based game.
- Iona is the only "Fleet of Fog" vessel that is shown to use warplanes offensively (happens in chapter 72). And as she controlled hers via direct immersion, the attack was quite effective.
- While neither Iona nor I-401 is directly present, Iona's voice replaces the standard announcer and adjutant's in the online naval action game World of Warships whenever an Arpeggio ship is in battle.