It is symbolical existence of the castle town of old Oka feudal clan that owned seventy thousand Koku. The Koku means the value of the official crop of rice that was used for the breadth of the land that one Koku equals about five bushels or about one hundred and eighty liters of unpolished rice.
The Numerize River flows through the south side, the Inaba River flows through the north side and they form a moat that is the natural fortress.
It was built the castle in 1185 by Ogata Saburokoreyoshi to invite Minamoto Yoshitsune.
However, Yoshitsune was shipwrecked in Daimotsunoura ,present Amagasaki, so he could not come. Another name of this castle is Gagyujo. This means the castle is like a cow that is lying down. The height above the sea level is 325 m.
This Castle that is on the Aso lava plateau didn't yield to the violent attack of the Shimazu army.
It is famous of the Kojonotusuki (Moon at the Ruined Castle) which Rentaro Taki composed.