There exists few twin cities around the world, most cities differ in one way or another with their neighboring cities, but such is not the case with Yokohama and Tōkyō.

At face value, these two cities can be seen as carbon copies of each other. Tōkyō and Yokohama are the largest and second largest cities respectively in terms of population size, they are both economically vital to the Japanese Empire, and they are both large port cities with hundreds of ships dropping anchor there each day.

The city's prominence as a port city can be traced back from near the end of the Edo period, and it is where Commodore Perry first landed and forced in the modern age.

Today, along with civilian ships, Yokohama is a major naval base for IJN fleets, enforcing the will of the Empire around the home islands as well as a base of operations for naval movements across the Co-Prosperity Sphere and the Pacific Ocean.