was an ancient ''

kōgoishi Kōgoishi (神篭石 or 神籠石) are earthenwork structures, on a stone foundation, constructed in Japan during the Asuka period, particularly in areas around Fukuoka, on the island of Kyūshū. The name "''kōgoishi''" means "stones of divine pr ...

'' type castle located in the city of

Sōja file:Bitchu Kokubunji, zenkei.jpg, 270px, Bitchū Kokubun-ji is a Cities of Japan, city located in Okayama Prefecture, Japan. , the city had an estimated population of 69,428 and a population density of 330 persons per km2. The total area of the ...

Okayama Prefecture is a Prefectures of Japan, prefecture of Japan located in the Chūgoku region of Honshu. Okayama Prefecture has a population of 1,826,059 (1 February 2025) and has a geographic area of 7,114 Square kilometre, km2 (2,746 sq mi). Okayama Prefecture ...

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

. Its ruins have been protected as a National Historic Site since 1986. Portions of the castle were reconstructed in the early 2000s.

Legend

The castle's name literally means "demon castle" (''ki'' is another reading for the character for ''

oni An ( ) is a kind of ''yōkai'', demon, orc, ogre, or troll in Japanese folklore. They are believed to live in caves or deep in the mountains or in hell. Oni are known for their superhuman strength and have been associated with powers like th ...

''); according to a traditional fable, a demon named ''Onra'' or Ura once ruled

Kibi Province was an ancient province or region of Japan, in the same area as Okayama Prefecture and eastern Hiroshima Prefecture. Nussbaum, Louis-Frédéric. (2005). "''Kibi''" in . It was sometimes called . It was divided into Bizen (備前), Bitchū (� ...

from the castle. The castle is the basis of the myth that is associated with the folklore hero,

Momotarō is a Folk hero, popular hero of Japanese folklore. His name is often translated as ''Peach Boy'', but is directly translated as ''Peach + Tarō (given name), Tarō'', a common Japanese given name. ''Momotarō'' is also the title of various books, ...

. The legendary story of Kibitsuhiko-no-mikoto and Ura explains that the Prince Ura of Kudara used to live in Ki-no-jo (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. However, "Ki'' means "castle'' in the ancient language of Baekje, and was later simply assigned the ''

kanji are logographic Chinese characters, adapted from Chinese family of scripts, Chinese script, used in the writing of Japanese language, Japanese. They were made a major part of the Japanese writing system during the time of Old Japanese and are ...

'' character for "demon''. "Ki-no-jō" is a name that combines the two words for "castle".

History

After the defeat of the combined

Baekje Baekje or Paekche (; ) was a Korean kingdom located in southwestern Korea from 18 BCE to 660 CE. It was one of the Three Kingdoms of Korea, together with Goguryeo and Silla. While the three kingdoms were in separate existence, Baekje had the h ...

and Yamato Japan forces, at the hands of the

Silla Silla (; Old Korean: wikt:徐羅伐#Old Korean, 徐羅伐, Yale romanization of Korean, Yale: Syerapel, Revised Romanization of Korean, RR: ''Seorabeol''; International Phonetic Alphabet, IPA: ) was a Korean kingdom that existed between ...

and

Tang China The Tang dynasty (, ; zh, c=唐朝), or the Tang Empire, was an Dynasties of China, imperial dynasty of China that ruled from 618 to 907, with an Wu Zhou, interregnum between 690 and 705. It was preceded by the Sui dynasty and followed ...

alliance at the

Battle of Hakusukinoe The Battle of Baekgang () or Battle of Baekgang-gu, also known as the Battle of Hakusukinoe () in Japan, and as the Battle of Baijiangkou ( zh, c=白江口之战, p=Bāijiāngkǒu Zhīzhàn, t=白江口之戰) in China, was a battle between Baek ...

in 663, the Yamato court feared an invasion from either or both Tang or Silla. In response,

Emperor Tenji , known first as and later as until his accession, was the 38th emperor of Japan who reigned from 668 to 671. He was the son of Emperor Jomei and Empress Kōgyoku (Empress Saimei), and his children included Empress Jitō, Empress Genmei, an ...

ordered the construction of a huge network of shore fortifications throughout the rest of the 600s, often with the assistance of Baekje engineers, generals and artisans. Unaware of the outbreak of the Silla-Tang War (670–76), the Japanese would continue to build fortifications until 701, after finding out that Silla was no longer friendly with Tang. According to the ''

Nihonshoki The or , sometimes translated as ''The Chronicles of Japan'', is the second-oldest book of classical Japanese history. It is more elaborate and detailed than the , the oldest, and has proven to be an important tool for historians and archaeol ...

'', 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). Ki Castle is not mentioned in any historical documents, and the year of its construction is unknown, but

archaeological excavation In archaeology, excavation is the exposure, processing and recording of archaeological remains. An excavation site or "dig" is the area being studied. These locations range from one to several areas at a time during a project and can be condu ...

s show that it was built in the latter half of the 7th century. The caste is situated at the southern end of the Kibi plateau and encompasses the summit of a mountain near the center of ancient Kibi Province. A wall made of stone and earthen ramparts with four gates, corner towers and six water gates, stretches for 2.8 kilometers. The area inside the wall is about 30 hectares. The discovery of paving stones to protect the castle walls was the first of its kind in Japan. Within the castle, the foundation stones for seven buildings, one raised pillar building, a reservoir and well, twelve forges and blacksmith workshop remains have been confirmed. While many of the contemporary ''kōgoishi'' fortifications appear to have been left unfinished, Ki Castle is equipped with most of the facilities necessary for a mountain castle, indicating its importance. The location of the castle overlooks the

Seto Inland Sea The , sometimes shortened to the Inland Sea, is the body of water separating Honshu, Shikoku, and Kyushu, three of the four main islands of Japan. It serves as a waterway connecting the Pacific Ocean to the Sea of Japan. It connects to Osaka Ba ...

, which was the main sea route for international exchange and trade and was therefore also the main route for an invader. Yashima Castle in Kiyama Castle, contemporary fortifications on the island of

Shikoku is the smallest of the List of islands of Japan#Main islands, four main islands of Japan. It is long and between at its widest. It has a population of 3.8 million, the least populated of Japan's four main islands. It is south of Honshu ...

are within the field of view of Ki Castle. Rammed earthworks measuring 7 meters wide and 6–7 meters high account for more than 80% of the castle walls. However, 1.5 meter wide paving stones are laid on the inside and outside of the bottom of the castle wall, giving it a strong atmosphere. The two overhangs on the front of the defenses are built with stone walls. Water gates to prevent the walls from collapsing due to running water are concentrated on the defensive front. There are four

sluice gate A sluice ( ) is a water channel containing a sluice gate, a type of lock to manage the water flow and water level. There are various types of sluice gates, including flap sluice gates and fan gates. Different depths are calculated when design s ...

s, with stone walls built 2 to 3 meters below the castle walls to provide water inlets, and earthworks on the tops of the water channels. The other two are percolation gates that allow water to flow naturally between the stone walls. In addition, embankment-like remains were excavated in two valleys on the castle side of the water gate to protect the castle walls from debris flows and running water and to secure water. There were four castle gates: the east, south, and west gates on the front of the defenses, and the north gate on the back of the defenses. The main entrance is the west gate, and it was protected by a corner tower. There is also a rammed-earth mound measuring about 300 meters in length, about 3 meters in height, and about 21 meters in width at the base located in the rural area where the low hills at the southern foot of Ki Castle protrude from the north and south. It is also believed to have been the site of a secondary fortification intended to protect the approach road to the castle. From the bottom of the wall many wooden products were unearthed, as well as

Sue ware was a blue-gray form of stoneware pottery fired at high temperature, which was produced in Japan and southern Korea during the Kofun, Nara, and Heian periods of Japanese history. It was initially used for funerary and ritual objects, and orig ...

and

Haji ware is a type of plain, unglazed, reddish-brown Japanese pottery or earthenware that was produced during the Kofun, Nara, and Heian periods of Japanese history. It was used for both ritual and utilitarian purposes, and many examples have been found ...

pottery, inkstones, whetstones, nails and other ironware. Relics related to Buddhism, such as tiled pagodas, water vases, and vessels, have been unearthed around the foundations of the buildings on the summit of the mountain. From these relics, it was determined that a Buddhist temple was constructed on the site from the

Asuka period The was a period in the history of Japan lasting from 538 to 710, although its beginning could be said to overlap with the preceding Kofun period. The Yamato period, Yamato polity evolved greatly during the Asuka period, which is named after the ...

to the

Heian period The is the last division of classical Japanese history, running from 794 to 1185. It followed the Nara period, beginning when the 50th emperor, Emperor Kammu, moved the capital of Japan to Heian-kyō (modern Kyoto). means in Japanese. It is a ...

after Ki Castle was abandoned as a fortification. In 1978, the first full-scale archaeological survey of the remains was undertaken. From the findings of this examination and excavated artifacts, it is believed that the castle was constructed in the Asuka period and was in operation for only a short time, from around the fourth quarter of the 7th century to the beginning of the 8th century, although it is also possible that the castle was built as early as 667 AD. Ki Castle was listed as one of

Japan's Top 100 Castles The Japanese castle, castles in were chosen based on their significance in culture, history, and in their regions by the in 2006. In 2017, the Japanese Castle Association created an additional finest 100 castles list as Continued Top 100 Japane ...

by the Japan Castle Foundation in 2006.Japan Castle Foundation
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Gallery

File:Kinojo_Nishimon.JPG, West Gate (outside the castle) File:鬼ノ城西門.jpg, West Gate (inside the castle) File:鬼ノ城角楼.jpg, Corner tower (outside the castle) File:北門（城外より）.jpg, North gate (outside the castle) File:鬼ノ城石垣.jpg, Ishigaki style File:鬼ノ城第二水門.jpg, Second water gate File:水城状遺構を望む（城内より）１.jpg, A view from the castle

References

Literature

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External links