Koka Castles

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The Castles of Koka


This article is a deep survey of the castles of the Koka region of Shiga Prefecture. They originally caught my interest because there were so many well preserved small castles in a compact area, but there was very little information about them in most books about castles and definitely none in English, anywhere. Occasionally, you will see other castle explorers visiting major sites like Wada Castle, Tsuchiyama Castle and Shingu Castle in a scattered approach but I have seen no holistic surveys in any language. As I started researching, it opened up so many fascinating windows into the history of this region and the part it played in the major events of the time. The origin of the Koka Ninja (often erroneously called the Koga Ninja) is also deeply rooted in the history of Koka. Since this is a castle website I start with a survey of castles but feel free to jump down to the history section and come back.

The 53 Koka Families 〜甲賀五十三家〜

The 53 clans of Koka ruled their territory semi-autonomously in a collective known as the Kokagunchuso (甲賀郡中惣). Each of the Koka families had roughly similar sized landholdings and each had an equal voice in governing the Koka lands. There were no vast territories nor subservient hierarchies to give rise to large scale castles either. They relied on each other for a unified defense and built many small castles around their territories to effectively create one giant impenetrable castle network with a nearly uncountable number of defensive positions. Within the 53 Families there were also sub-groups of families and alliances such as the Wada, Hattori, Mochizuki, Ohhara and Ban that managed local affairs on a smaller level. Some books or articles that only briefly talk about the Koka region claim it to be subservient to the Rokkaku at Kannonji Castle. While some Koka samurai did serve as retainers to the Rokkaku, the Kokagunchuso alliance considered themselves independent and important allies to the Rokkaku.

The Castles of Koka 〜甲賀の城館〜 


Over 300 castles and fortified homes (yakata) were built across these lands. Some of these castles have been lost to time but traces of the original castle, either above ground or uncovered through archeological surveys, have been identified for around 180, the highest concentration of castles anywhere in Japan. If anyone tried to invade the lands they would have to take each castle one at a time slowly moving inward. If you ignored any one fortification (or didn't realize it was there!) you would run the risk of it being used to attack you from behind. This defensive collective and castle network was the only one of it's kind in Japan. The Iga region in Mie, just across the border and mountains, is similar but not as large nor dense as Koka.

It would be nice to say that the Koka castle network evolved from a benevolent agreement for mutual defense, but if that were really the case, it should have been a more coordinated approach across the region and there would not have been the need for this many small castles in an unorganized manner. The origins of the castle network started from the need for local samurai to protect their own holdings from nearby samurai with similar sized lands and no particularly strong leader emerging among them. Each castle is just big enough to be built and maintained by the landholder. Branch families and close neighbors created alliances which were eventually combined into the larger alliance of 53 families.

Yakatajiro 〜館城〜

The castles of the koka samurai primarily fall into the category of "single bailey" (単郭方形 たんかく ほうけい) castles and more specifically (単郭方形四方土塁 たんかく ほうけい しほう どるい). In other words, square single bailey castles with earthen embankments on four sides. The typical castle has a main bailey roughly 30-50 sq meters. Some of the biggest ones at Mochizuki Castle and Shingu Castle have embankments over 8 meters high. Similar single bailey (単郭方形) castles exist around the country but tend to be the much smaller fortified residences (yakata) of local lords and landholders. Koka and Iga are unique in that they are the only places where this design was scaled up to this "castle level", not simply a yakata. For this reason they are sometimes called yakatajiro (館城) to highlight their origin, but to emphasize that they are the scale of castles, not simply yakata. Despite their comparatively smaller size, the amount of organization and construction required to build and maintain this number of castles meets or exceeds the requirements of many larger castles of the time. Today it is easy to look at these small earthworks castles and think of them as simply temporary forts or borderlands castles with few structures but excavations have found the foundations of buildings, watchtowers (seiroyagura), and clay tiles indicating they were well fortified and developed to withstand a longer siege.


This illustration shows one of the typical more developed Koka yakatajiro. The large main bailey is a square with earthen embankments on all sides. It includes a main entrance and one optional back entrance. Around the castle is a trench and along the outside you may find an additional earthen embankment. To further protect the main entrance an additional small bailey like a masugata or umadashi has been added. The roughly flattened area in front of the castle may have an underdeveloped supporting bailey. This illustration is partially based on Tsuchiyama Castle.

Shimoyama Castle is considered to be a good example of a well preserved Koka castle that closely retains the original square yakatajiro structure. The site is easy to access and well maintained making it a perfect place to kick off your exploration of Koka castles. The additional baileys, really just leveled open spaces outside the main castle, seem like a convenience rather than a planned part of the castle and have no particular defenses of their own.

From this basic yakatajiro design, the Koka castles were often expanded with additional layers of smaller baileys and trenches around the outside for further fortification. Some of the best examples are to be seen at Shingu Castle, Mochizuki Castle and Wada Castle. These castles in particular may have been expanded even beyond typical measures because of the roles they played in the greater historical events of the time (see history below).

I would note one other difference that is not necessarily highlighted in the literature but is obvious after visiting many Koka castles. Some of the yakatajiro on mountains or hillsides actually seem to have been carved from the mountain, rather than piling up earth to create embankments. Shimoyama Castle also fits into this category. It is really a large hill, but one long trench separates the castle area from the non castle area. The interior of the castle that would be considered the honmaru has been carved out so the base is actually at a lower elevation and the surrounding walls which are what's left behind from the mountain. Certainly those castles on plains were built in the more traditional way but for those that have been carved from the mountain it also offers greater variety in extra fortifications that allow castles to take advantage of elevation and topographical features of the location. One feature that intrigued me at several sites was a kind of long defensible obikuruwa or dorui type wall outside the honmaru that follows the incline of the hill. Shingushi Castle and Mochizukishi Castle are great examples. There is also the long Ninokuruwa Bailey at Ueno Castle where it seems to shield or hide the castle behind it.

Castle Pairs 〜二城並立型〜

I'm sure this is a horrible translation, but for now we'll go with 'Castle Pairs'. Reading the literature about Koka Castles or visiting many of them you will see that there are many instances where two castles are very close to each other about 50-100m away. This is common in the Koka area where two castles are built near each other essentially acting as one big castle. Each however is an independently developed yakatajiro design and not directly connected. One is typically a little larger and more developed and may be considered the main castle while the other is a little less developed and is the supporting castle: 支城 (しじょう) or 出城 (でじろ). This structure is known as 二城並立型 (にじょう へいりつがた) or 二城近接型 (にじょう きんせつがた).

Well known examples on this site include: Mochizuki Castle & Mochizukishi Castle, Shingu Castle & Shingushi Castle, and Maruoka Castle & Higashi Maruoka Castle.


Higashimukaiyama Castle & Nishimukaiyama Castle (not currently accessible)

Mountain Castles of Koka 〜甲賀の山城〜

Along the borders of the Koka region you will also find some more traditional mountaintop castles that fortified the borders too. Mikumo Castle which sits at the entrance of the Koka region is a great example. Ogawa Castle on the border with Nara and Mie is another mountaintop castle and also paired with a yakatajiro (Ogawa Nishinojo Castle) in the valley below. The castles of the Umasugi on the western border and those of the Horikita on the Eastern border fall into this category too but I don't have any to share yet. One theory said that due to the extreme importance of the Koka region to the Rokkaku, they advised or influenced the development of these mountaintop fortresses to help protect the borders. This is also evidenced in the stone walls at Mikumo Castle that are reminiscent of Kannonji Castle.

Visiting Koka Castles 〜甲賀の城を訪ねる〜 

Loading map...

Map of castles currently on Jcastle.info

Several of the best Koka castle sites were designated "National Historic Sites of the Kokagunchuso" in 2008 and are well maintained including Shingu Castle, Shingushi Castle, Jizen Castle, Murasame Castle and Takenaka Castle. The Wada castles are also well preserved and signposted. The other profiles you see here tend to focus on those that have more ruins to see.

Tsuchiyama Castle (yakatajiro castle)

Ogawa Castle (mountaintop castle)

Many of the smaller sites are on private property and not specially preserved nor open to visitors casually walking through. In fact, some are so overgrown it may be difficult to find an entrance or move around to see the ruins through the forest (e.g. Shimoyama Kita Castle). Those that were located on plains or in more populated areas tend to have been completely developed over and have nothing to see. I visited a few that have become factories or farm fields, but they are not documented here simply because there was nothing to see or it is hidden behind an area that is posted as no trespassing (Higashimukaiyama Castle, Nishimukaiyama Castle). For those on private property, be respectful and ask permission were practical. I was actually declined at one where the farmer was outside in his field (Tsuyama Castle), which is why you only see one photo from a distance. On the other hand, the property owner of another (Uchikoshi Castle) was very knowledgable, a retired teacher, and a member of the local ninja tourism association. We had a great chat along with his personal tour of the site. He also provided some tips for future travels and reiterated the point about private properties.

These are all the Koka Castles currently listed on Jcastle.info. This includes only those castles attributed to the 53 clans (e.g. no Minakuchi Castle. It mostly includes castles I visited personally (36) and a few contributed by ART and RaymondW.

  1. Ayukawa Castle (Koka)
  2. Beffu Castle (Koka)
  3. Hattori Castle (Koka)
  4. Higashi Maruoka Castle (Koka)
  5. Hodarakuji Castle
  6. Ichibajin'yama Castle (Koka)
  7. Jizen Castle (Koka)
  8. Kuboyashiki (Koka)
  9. Kuboyashikishi Castle (Koka)
  10. Kuraji Castle (Koka)
  11. Kurokawashi Castle (Koka)
  12. Maruoka Castle (Koka)
  13. Mikumo Castle (Koka)
  14. Mochizuki Castle (Koka)
  15. Mochizukishi Castle (Koka)
  16. Murasame Castle (Koka)
  17. Nishi Aoki Castle
  18. Ogawa Castle (Koka)
  19. Ogawa Nakanojo Castle (Koka)
  20. Ogawa Nishinojo Castle (Koka)
  21. Ohkawarashi Castle (Koka)
  22. Oki Castle (Koka)
  23. Okishi Castle III (Koka)
  24. Oohara Castle
  25. Shimoyama Castle (Koka)
  26. Shimoyama Kita Castle (Koka)
  27. Shingu Castle (Koka)
  28. Shingushi Castle (Koka)
  29. Takao Castle (Koka)
  30. Takenaka Castle (Koka)
  31. Tonoyama Castle (Koka)
  32. Tsuchiyama Castle (Koka)
  33. Tsuyama Castle (Koka)
  34. Uchikoshi Castle (Koka)
  35. Ue Castle (Koka)
  36. Ueno Castle (Koka)
  37. Wada Castle (Koka)
  38. Wadashi Castle I (Koka)
  39. Wadashi Castle II (Koka)
  40. Wadashi Castle III (Koka)
  41. Yamanaka Yashiki (Koka)

Koka Samurai In History 〜歴史で見る甲賀侍〜

The Koka families allied themselves with the Sasaki Rokkaku. Some of the local samurai were employed by the Rokkaku but the region was not subservient to them. The Koka Families kept their distance and considered themselves allies. When the Rokkaku were attacked by the Ashikaga Shogun (Yoshihisa) in 1487 for resisting Ashikaga rule (Oumi Magari no Jin) Rokkaku Takayori himself holed up in Koka instead of Kannonji Castle. The guerilla warfare employed by the Koka samurai helped withstand the Ashikaga for 3 years until the shogun died and the Ashikaga relented. The 53 families that supported the Rokkaku in this conflict became known as the 53 families of Koka. For their service during this conflict 21 of these families received commendation from the Rokkaku and were also known as the 21 Families of Koka attaining an elite status among the 53. The Koka samurai again supported the Rokkaku 5 yrs later (1492) in another siege by the Ashikaga and helped the Rokkaku escape through the Koka mountains and into Ise.

The Koka samurai's skill at guerilla warfare during these conflicts earned them much notoriety and is the origin of the Koka Ninja. It is from this time that local samurai started to be hired out as spies rather than make a meager living off the lands. In particular, the previously mentioned 21 Families of Koka are thought to be the origins of the Koka Ninja. They were not actually called ninja at the time, they were called shinobi, Koka samurai, Koka bushi or Koka no mono. The Koka region of Shiga was well known for medicinal herbs so the Koka spies specialized in disguising themselves as medicine sellers while traveling. Medicine sellers had access to a wide range of classes of people, thus extending their reach for gathering information. Medicine sellers often travelled far and wide collecting herbs, so they could easily justify their travels too, the perfect disguise. The Mochizuki Residence is the home of the former head of the Mochizuki clan and leader of the 53 Families. Here you will find much history about the medicine trade and origins of the Koka ninja.

The Koka Samurai however were not simply ninja and spies. They became professional soldiers and special forces. Their skill with guns, firepowder, guerilla tactics and castle building were in high demand across the country. The alliances among the families of Koka provided stability in their homelands which allowed them flexibility to leave their homes as professional soldiers. Some Koka samurai such as Wada Koremasa, Takigawa Kazumasa, and Yamanaka Nagatoshi would go on to become famous military commanders themselves and many others from Koka also served as military specialists.

Finally, when Nobunaga started to assail Rokkaku territories (1568-1573) Rokkaku Yoshikata again fled to the Koka region. He found refuge with the Mikumo and Mochizuki after the fall of Kannonji Castle and hid out in the Sugitani/Shinji Castle network (Mochizuki Castle, Mochizukishi Castle. Shingu Castle, Shingushi Castle, Jizen Castle, Murasame Castle, Sugitani Castle, etc). Mochizuki also helped to secure an escape route for the Rokkaku through his allies in Iga. One theory said that the reason the Rokkaku were finally defeated by Nobunaga is because the allegiance of some of the Koka samurai was won over by Tokugawa Ieyasu who influenced them not to interfere.

The events surrounding the fall of the Rokkaku and the rise of Oda Nobunaga caused the tightly knit Koka Alliance to start to weaken. Following the Honnoji Incident some Koka samurai (see Ogawa Castle) helped Tokugawa Ieyasu escape through Koka and Iga (famously called the Iga Crossing). They were rewarded with the rank of Hatamoto and fought by his side in The Battle of Komaki & Nagakute against Hideyoshi. The allied families of Koka represented everything Hideyoshi was against. They were local farmer/samurai, they allied with Tokugawa, and the Koka Alliance was a direct threat to his centralized totalitarian rule. Hideyoshi oppressed Koka, confiscated territories, and reassigned samurai. This was known as the Koka-yure (甲賀揺れ) or Koka-kuzure (甲賀崩れ). Hideyoshi also built Minakuchi Okayama Castle in the Koka region to exert his power and control.

The Koka samurai were considerably weakened under Hideyoshi but they regained some of their status with Tokugawa Ieyasu. At the Battle of Fushimi Castle, a precursor to the Battle of Sekigahara, the Koka samurai who fought for the Tokugawa suffered devastating losses. They were also effectively deployed for espionage during the Battle of Sekigahara. For their great service, Tokugawa formed 100 small groups in Koka from the survivors and their families. Around 30 years later he moved them to Aoyama in Tokyo where they became trusted guards of Edo Castle as the "Koka Gumi".

Postscript & Bibliography 〜後書き〜 

Despite their relatively small size and the many other magnificent castles around Shiga, the Koka castles should not be overlooked by castle explorers. I hope I have been able to convey some of my interest in these sites and maybe catch your interest too. I think I've covered all the key sites in Koka and sufficiently told the story of the Koka Samurai. There are a few pockets of castles I would like to visit yet when the nostalgic mood for Koka castles strikes me again, but for now I will move on to other projects.

Finally, I owe a big thanks to RaymondW and his wife who first lured me into the Koka region and trapped me in the depths of Koka history while accompanying me on many of these visits.

There is not much quality information on the internet about these sites. Even Japanese information seems to be shallow and frequently repeating the same few sources. I did a lot of extra research (including trips to the library!) to dig into the sources below. I hope this fills a niche in the English literature about these castles. I will certainly keep adding to this article and the collection of Koka Castles as I visit more in the future. Koka City is updating Vol.7 of their city history book (see below) dedicated to the castles of Koka. I'll be sure to get a copy when it comes out and see if it inspires me to document anything new.

July 8, 2023

© This article is copyright by Jcastle.info. Please do not reproduce without permission. If you use any quotes, ideas or context from here please provide credit and a link.

  1. 甲賀市史 vols II & VII
  2. 近畿の城郭
  3. 近畿の名城を歩く
  4. 近江の平城
  5. 近江の山城
  6. Koka City Pamphlets

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