Koto is the imperial city of the Samurai. With how unstable the Myre is, there are only a few locations that is safe to build a permanent structure on. Koto is built on one of those places, a high mesa that sits above the water line, connected to the land by a single bridge.
Koto is a prosperous city. The Seventh Emperor had a river diverted through it to power their machinery, carry away waste, and irrigate gardens.
Koto is also houses the Imperial Palace built by the Second Emperor. It was not always located in Koto. The original Imperial Palace was located elsewhere but the Emperor was driven by unknown forces to build it in Koto instead.
While Koto belongs to the Samurai, it was not first constructed by them. It was actually first constructed by a different unknown group. At some point of time the Knights would hold the city. Eventually, it would fall into the hands of the Samurai.
Koto did not always house the Imperial Palace, but at some point of time the First Emperor would be driven by an unknown force. The Second Emperor would build the Imperial Palace in Koto to celebrate his own glory.
The Orochi had become infamous for speaking out of turn against the Emperor. Furious at the insubordination, the Emperor imprisoned The Orochi in a cell in the lower half of the city.
General Tozen was tasked with defending the city. With a single bridge as an entrance, it could have been an easy task. However, after being unchallenged for so long, the Samurai forces guarding Koto had become stagnant and their numbers diminished. By the time of The Great Raid, they were too few to hold the bridge. Tozen attempted to repel the invaders by trapping them on the bridge and attacking their flank, but he was killed in battle against The Raider. Seeing their leader fall, the Samurai retreated. With its forces crumbled, the Vikings plundered the city.
With Koto in chaos, Ayu, Momiji, and Okuma took this opportunity to free The Orochi from prison. Together, they drove the Vikings out of Koto. But as they closed the doors to the city, the Blackstone Legion came charging in and made its way to the Imperial Palace, where they slayed the Emperor.