At the end of 7th century, Toyo no Kuni or Toyo Kuni (豊国) was split into Buzen, lit. front of Toyo and Bungo, lit. back of Toyo. Until the Heian period, Bungo was read as Toyokuni no Michi no Shiri. During theSengoku period, Bungo was a stronghold of the Otomo clan.
It is believed that the capital of Bungo was located in the Kokokufu(古国府) area, lit. old capital, of Oita, Oita but to this day, no remains have been found.