Submarine I-400
Mental Model | Vessel
I400 s2
Japanese name イ-400
First appearance:
Manga Chapter 9
Anime Episode 3
Mental Model information:
Status Active (manga);
Unknown (MIA) (anime)
Affiliation "Fleet of Fog", self
Mental Model's Appearance:
Eye color Green
Hair color White (manga);
Pink (anime)
Vessel Status:
Status Active (manga);
Sunk (anime)
Sunk by I-401 (anime)
Vessel information:
Type "Fleet of Fog" Sen-toku class submarine
Displacement 3,570/6570 tons
Length 122 m
Beam 12 m
Draft 9.7 m
Maximal Speed 80 knots
Armament 8x Torpedo tubes;
11x Photon cannons;
18x Missile launchers
Wave-Force Armor yes
Voice Actors:
Japanese Hidaka Rina
German Unknown

I-400 is a "Fleet of Fog" submarine and a personal guard and attendant of the supreme flagship Yamato.

Submarine I-400Edit

I-400 is a "Fleet of Fog" reincarnation a of Sen-toku class WWII Japanese submarine, upgraded with "Fog" technology. She has two sisters, I-401 and I-402, the latter one being her partner.

I-400 is almost identical to I-401 in her hull's appearance in manga, but has pinkish color scheme instead of a blue one in anime.

As a surveillance submarine, I-400 has a comparably small arsenal inboard: 8 frontal torpedo tubes and some small Photon cannons for active anti-missile defense system. However, she's equipped with detectors unparalleled by all others save for her sister I-402.

She and I-402 also seem to have a weird ability to block their sister vessels' (I-401) abilities to control their nanomaterials, thus preventing them from performing emergency repairs on the battlefield. It is not clear, whether this ability would work on any other vessel, though.

I-400 has a moderately powerful Wave-Force armor, which is capable of protecting her from a single shot from a heavy cruiser's Super-Graviton Cannon.

Mental modelEdit

I-400 has one Mental Model. She appears to be a girl in her late pre-teens with white (pinkish in anime) hair and green eyes. Her build is very similar to that of Iona or I-402, which is a bit surprising, considering that the other known sets of 'sisters' usually look quite different from each other.

The clothes that I-400 is wearing vary as she often falls prey to Yamato's bouts of fashion designing. However, it appears that she prefers purplish and pinkish colors with blue or yellow details.

In manga I-400 is polite and completely loyal to Yamato. She's not very talkative - but is a good spy, both as a submarine and as a Mental Model - so that is something to be expected.

In anime, being an entity without any known superiors, I-400 is a bit more talkative, often speaking in turns with her sister I-402 with whom she appears to be sailing together at all times.

Role : MangaEdit

In the early chapters I-400, along with her sister I-402, are sent to confront Takao who had just deserted the "Fleet of Fog". They managed to track her down in the capital of Northern region, however, they deemed her to no threat to the fleet at the moment and allowed her to live.

After that, for some time the two sisters were shifted into tracking down the recently-reappeared Admiralty Code, however, this mission was soon aborted. I-400 was ordered to tail heavy cruiser Maya with Haruna and Kirishima inboard. I-400 managed to follow them all the way back to the Northern region without being discovered. There, she continued to spy on them as a Mental Model. I-400 was a witness of Haruna confronting Makie inside the Chihaya residence.

Following Haruna's departure from New Hakodate, she too relocates to Yokosuka city. Surprisingly enough, she does this by using a seaplane. According to the dialogue that happens between her, I-402 and Zuikaku, I-400 is one of the few "Fleet of Fog" vessels to still have seaplanes in her arsenal.

While staying at Yokosuka, I-400 has been spying on the Japanese government, eventually finding out that they know - or at least suspect - that she, I-402 and Zuikaku are Mental Model. This revelation prompts I-402 to initiate an open contact with the humans.

Along with her sister, I-402, I-400 has a long-term mission that is collecting the information about the Admiralty Code for Yamato.

Role : AnimeEdit

Up until Kongou's attack on Iwo Jima, I-400 and her sister I-402 seemed to be the same as in manga, however it was then revealed that their purpose here was entirely different. Instead of being supreme flagship's eyes and ears, these two submarines are actually autonomous unit with high-enough standing within the "Fleet of Fog" to be able to freely replace Kongou as the flagships of the First Oriental fleet.

They also seem to be far more proactive in anime, and it was them, who sunk I-401 after she managed to break through Kongou's blockade around Iwo Jima. When I-400 and I-402 learned that I-401 was saved by Takao, the two of them personally went after her again, but were defeated and sunk shortly afterward.


  • Yamato - The supreme flagship of the "Fleet of Fog" is I-400's mistress and commander.
  • I-401 - I-400's rebellious sister. I-400 doesn't really understand why Yamato allows I-401 to do what she does, but she does follow Yamato's order of leaving her to her own devices.
  • I-402 - I-400's other sister and her partner on many missions. They have joined cores; supposedly this makes them more dangerous when they are together.


  • According to the after-chapter 4-panel comics, I-400's New Year wish is a proper name for her Mental Model.
  • According to the after-chapter 4-panel comics, I-400 and I-402 missed the Admiralty Code holder at least once. How can one not notice someone walking around in a complete spacesuit is unclear.
  • According to the after-chapter dialogues, because I-402 is an otaku-girl, I-400 calls her the first NEET of the "Fleet of Fog".
  • I-400 is one of the few "Fleet of Fog" vessels to still have seaplanes in her arsenal - since seaplanes do not have Wave-Force armor, they could not stand up to human fighter jets and were subsequently removed from the fleet's arsenal.
  • Being an I-400 class submarine, I-400 (the WWII one) was one of the biggest diesel submarines ever built. Submarines of this class are biggest submarines of the WWII.


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