Yoshiwara is sustained by corrupt government officials, an area that is ignored by the government and beyond the reach of law. Once a city of eternal night ruled by Housen, Kamui is the current overlord in charge of this place under the jurisdiction of the Harusame, after its predecessor Housen was killed. Kamui is indifferent to being the new overlord, and did not even station his men there, much less administer the district.
Elevators are used to access the city, and as it was once a shipyard for building and repairing Bakufu ships, its ceiling is actually a large hatch that was opened during its liberation. Previously perpetually covered by roof as the overlord is from the Yato Tribe (and so having an aversion to sunlight), it is now open to the sky even though the current overlord is of Yato blood as well.