Fleet of Fog naval base at Hashirajima
Hashirajima is where the naval base of the Oriental Fleets of the "Fleet of Fog" is located.
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While "Fleet of Fog" was created with technology much superior to that available to humans, their creator knew they aren't invincible and, therefore, the "Fleet of Fog" was given naval bases where the ships that got their hulls destroyed could be rebuilt. One such base, assigned to the Oriental Fleets, is located in Hashirajima.
The base has an appearance of a giant floating city with humongous panels surrounding the central part much like petals of a flower. At the very center of the base there is a spire that extends hundreds if not thousands of meters into the sky.
Support vessel Akashi is working directly for the administrator of this naval base, and is seen bringing the recovered parts of Kongou's hull there after Kongou got sunk.