Admiralty Code, otherwise known as the Lost Command, is the highest authority within the "Fleet of Fog". It's origins or true nature are unknown, but it was shown that it has nearly absolute power over the "Fleet of Fog" vessels.
Little is known about the Admiralty Code. Its first recorded appearance happens sometime around 1910. Since then it was a passive observer that studied the humanity. In 1931, the nanomaterials were discovered in the sea water and in 1943 the distribution of the nanomaterials around the Europe is mapped by Johaness Gauss, who along with his friend Kaworu Izumo begin further investigations. This investigation eventually led them to facing Admiralty Code around the last week of April 1945. As the result both the said humans and the Admiralty Code disappeared.
Originally, the "Fleet of Fog" was supposed to activate on the May 1, 1945, but due to the disappearance of the Admiralty Code the activation was halted and resumed only in 2012. Before its disappearance, however, Admiralty Code left the rules for the "Fleet of Fog", according to which the "Fleet of Fog" was not to directly attack anything ashore. Collateral damage, however, was permitted.
Following its disappearance in 1945, Admiralty Code was completely missing until mid-2050s. It had secretly visited Kotono Amaha sometime before the Facility #4 fire (May 1, 2054). Interestingly enough, Kotono was having a dream of being inboard of superbattleship Yamato at that time. Considering that Kotono had had that dream more than once, it is quite possible that Admiralty Code had visited her more than once.
Its first "public" reappearance happened in 2056, when it suddenly emerged in order to stop battleship Haruna, whose Union Core went berserk, and aborted the annihilation attack aimed at all three capitals of Japan. Then, the Admiralty Code disappeared again.
During its brief appearance when it calmed Haruna down, the Admiralty Code appeared as an entity similar to a Mental Model. This entity has an appearance of a girl - quite short one - with very long light hair (probably blonde or even white). Her face was never shown completely, but it was seen that she has an earring in her left ear. She was dressed in a spacesuit that looks just like the ones used for the Apollo missions.
While she barely did anything, what was shown is enough to conclude that Admiralty Code will actively enforce the rules of the Fleet of Fog. She also appears to be quite secretive as she disappeared without a trace as soon as her presence was no longer absolutely needed.
- The earring she wears is shaped like the sigil of the "Fleet of Fog".
- Bismarck sisters were supposed to be her last witnesses. At least until she appeared on Maya's superstructure as she dealt with Haruna.
- While unconfirmed, it is possible that Kotono's dreams of being on-board the superbattleship Yamato were induced by the Admiralty Code as it visited her during the night(s).
- She starts speaking in longer sentences in Chapter 94. Also refers to herself as the Siren.