備前國
Before the Muromachi period, Okayama was one corner of a farm region and included a small castle built by the Kanemitsu. In the Sengoku period, Ukita Naoie attacked Okayama and attacked the castle for the transportation resources and extensive farmland in the region. Naoie remodeled the castle, built the old Sanyo road to the central part of the castle town, and called in craftsmen both from inside and outside of Bizen Province. Okayama became the political and economical capital of Bizen Province.