Ki Castle

Ki Castle 鬼ノ城
Kijō Mountain, Sōja, Okayama Prefecture, Japan
The Nishimon (Western Gate) of Kinojō, and surrounding area, restored in 2004.
Type	Korean-style fortress
Site information
Controlled by	Japan
Condition	Active archaeological site, some buildings reconstructed
Site history
Built	7th century, partially reconstructed 2000s
Built by	Yamato court
Materials	wood, earthworks, stone

Ki castle (鬼ノ城, Ki no jō^?) was a Japanese castle of the kōgoishi type, constructed in the late 7th century by the Yamato Imperial court. The site, atop Kijō Mountain in what is today the Okayama Prefecture town of Sōja, is considered a national monument. Portions of the castle were reconstructed in the early 2000s.

The castle's name literally means "demon castle" (ki is another reading for the character for oni); according to a traditional fable, a demon named Onra or Ura once ruled Kibi Province from the castle.

The castle is the basis of the myth that is associated with the folklore hero, Momotarō. The legendary story of Kibitsuhiko-no-mikoto and Ura explains that the Prince Ura of Kudara used to live in Kinojo (castle of the devil) and was a cause of trouble for the people living in the village. The emperor's government sent Kibitsuhiko-no-mikoto (Momotarō) to defeat Ura.

Following the defeat of Yamato Japan in the 663 battle of Hakusukinoe by an alliance of Tang China and the Korean kingdom of Silla, Emperor Tenji ordered the construction of defenses against a possible invasion. According to the Nihonshoki, twelve Korean-style mountain fortifications were built in western Japan at this time, and it is believed that Ki castle was one of them. The identification of particular sites with the fortresses constructed at this time remains a subject of debate, and most fortifications of this period are classified under the wider term kōgoishi (神籠石).