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Castle Koyama Castle

This article is in the series Walking the Japanese Castles
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Kōyama Castle (高山城 Kōyamajō) is a mountain castle in Kimotsuki located in the centre of Ōsumi Peninsula (大隅半島). It was the base of the local Kimotsuki clan who ruled this area until the end of the Sengoku Period and is also known as Kimotsuki Castle (肝付城 Kimotsukijō). The castle is a National Historic Site (国の史跡 Kuni no shiseki).

Kōyama Castle (高山城) 01


In the year 969, Tomo Kaneyuki (伴兼行) was appointed a land steward (荘園監督官 shōen kantoku-kan) in Satsuma Province. His grandson Kanesada (兼貞) was posted at Kimotsuki County as an official of Ōsumi Province. Kanesada's son Kanetoshi (兼俊) adopted the name of the locality as his surname and called himself Kimotsuki. Supported by the fertile lands of the Kimotsuki River basin, the clan continually increased its regional influence. It is not clear when Kōyama Castle was built, but according to old records, Shimazu Tadamasa (島津忠昌, 1463-1508) attacked the 14th lord Kanehisa (兼久) who was holed up at the castle in 1506. The 16th lord Kanetsugu (兼続) further consolidated his power by siding with the Itō against the Shimazu. In 1562, he conquered Shibushi Castle and achieved the clan's largest territorial expansion. However, the Shimazu soon counterattacked and in 1566, their impregnable stronghold at Kōyama Castle finally fell. Subsequently, the Kimotsuki surrendered to the Shimazu. The 550 years of Kimotsuki rule in Ōsumi came to an end.

The castle consisted of the Honmaru (本丸), the Ninomaru (二の丸), Yamabushi Castle (山伏城) and the Oku-kuruwa (奥曲輪), all divided by dry moats. In the lowlands on the west side of the castle, were a samurai alley (士小路 Shikōji), an archery ground (弓場地 Yubaji), and horse riding grounds (馬乗馬場): Kōyama Castle was a huge fortress comprising a total area of 50 hectares.

Kōyama Castle (高山城) 02.jpg

I was wondering whether Kōyama Castle was really impenetrable. Indeed, the castle was a stronghold that utilized the deep valleys engraved into shirasu-daichi (シラス台地, pyroclastic plateaus); two rivers flow to the north and south. On the other hand, Chiran Castle or Shibushi Castle had similar defences. In other words, Kōyama Castle was not so special. As you see in the top picture, it looks quite ordinary. So why was this castle considered impregnable? Reducing the scale level of the map and watching the surrounding topography ...

Kōyama Castle (高山城) 03.jpg

Based on a map of the Geospatial Information Authority of Japan. The location of the enclosures is estimated.

... I noticed that the river and the mountains surround the entire castle.

The mountains to the northwest face the plain and are especially straight and steep: natural earthworks forming a natural fortress that offered the enemy a very limited angle of attack. I found an old map* that depicted the surrounding mountains and makes it clear that the mountains are a part of the castle. Understanding its exceptional topography I was convinced that it was impregnable.


*The Map was provided by the Ōsumi office of the Ministry of Land, Infrastructure and Transport and explains not only the history of the castle but that of Kimotsuki River, too.

I arrived at Kōyama from Shibushi Castle. This signboard mentioned the "designated important cultural property Kōyama Castle", but I am afraid it isn't. I parked my car at the site of the former Honjo Elementary School.

Kōyama Castle (高山城) 04.jpg

A sign warned of hornet nests with the proviso that "visitors can enter the Honmaru". The warning was in handwriting, so I doubted its authenticity. I decided to enter anyhow.

Kōyama Castle (高山城) 05.jpg

① Otemon (大手口, Main Gate)

Kōyama Castle (高山城) 06.jpg

② Kuma Residence (球麻屋敷)

In 1506, the Sagara army that had come to the castle from Kuma County to provide reinforcements to Shimazu Tadamasa camped at this residence.

Kōyama Castle (高山城) 07.jpg

Otemon (Main Gate) is just in front of Ninomaru.

Kōyama Castle (高山城) 08.jpg

The path is basically straight. The lines of tall cedars are impressive.

Kōyama Castle (高山城) 09.jpg

③ Yamabushi Castle (山伏城 )

This enclosure was the place where yamabushi (itinerant monks) stayed.

Kōyama Castle (高山城) 10.jpg

The site of the moat

Kōyama Castle (高山城) 11.jpg

④ Ninomaru (二の丸跡)

Kōyama Castle (高山城) 12.jpg

The entrance to the Masugata enclosure on the north side of the Honmaru.

Kōyama Castle (高山城) 13.jpg

⑤ Honmaru (本丸)

Some earthworks surrounding the enclosure survived.

Kōyama Castle (高山城) 14.jpg

Fearing the hornets, I returned here. There are more enclosures on the back of the castle.

Date of visit: 21 October 2013


  • Address: 8355 Niitomi, Kimotsuki, Kimotsuki District, Kagoshima 893-1207
  • Access: 42km from Higashi-Kyushu Expressway Soo-Yagoro Interchange via Prefectural Route 561
  • Parking: at former Honjo Elementary School (Spot 'P' pointed in the map above)
Next article in the series 'Walking the Japanese Castles': Mukasa Castle
Previous article in the series 'Walking the Japanese Castles': Shibushi Castle
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Hiroto Uehara
Hiroto is an ordinary Japanese office worker, but his true mission is searching for castles on the weekend.


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Hiroto Uehara
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〒893-1207 鹿児島県肝属郡肝付町新富8355

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