Kozutsumi Castle

From Jcastle.info

Kozutsumijou (1).JPG


Koźutsumijō is thought to have been first built by the Nagahara Clan in the late 15th century when they were vassals of the Rokkaku Clan. See my article on Nagahara Castle for more information about that clan. The Tanaka Clan are also thought to have been castellans under the Rokkaku Clan. Koźutsumijō is a very large site and it has an advanced structure and defensive layout, which makes me uneasy about such an early date for its construction. In 1568 Oda Nobunaga invaded Ōmi and the Nagahara betrayed their Rokkaku masters. What if the castle's current layout dates to during or after this time period? It's possible, if not likely, that the castle was rebuilt either in preparation for Oda's invasion by the Rokkaku, or by Oda himself for the pacification of Ōmi, including Kōka, and Iga.

Visit Notes

Koźutsumijō, also called Koźutsumishiroyamajō for some reason, was the main destination of my brief tour of sites in Yasu. It is an expansive yamajiro (mountaintop castle) with lots of ishigaki (stone-piled ramparts) and other interesting features. I think this site is not so well known despite its compelling ruins, but then it does have to compete in a prefecture / province full of amazing castle sites. What's intriguing about this site is that the topmost baileys appear as a fairly basic mountaintop fort, and most of the impressive sights are below.

When I first hiked up I identified the top baileys and thought 'is this it?' because I had expected a little more from what I'd seen online. If i didn't have a map with me I might've missed all of the best parts of the castle! It's not usual that the highest situated baileys at a castle are the least interesting. That said, the rear of the topmost bailey is a very steep track made up of large boulders. On my descent I completely missed it, and so I had to climb back up, but there is ishigaki between boulders around the side of this top bailey. Once I found this ishigaki I suddenly understood: this unassuming set of baileys is just the tip of an iceberg; the rest of the castle is around five times larger.

Although ishigaki segments can be found in a handful (I guess this means 'five or so') of places, the remains around bailey fourteen (there are a lot of baileys) are probably the most impressive. I say 'probably' because the map I was using had one bailey missing! According to another map, which admittedly is the one shown on the explanation board at the bottom of the site and so I am sorry to have not noticed the descrepency, there is another bailey with ishigaki. Guess I'm going back!

The main bailey, the largest bailey, also labelled 'bailey thirteen' on the site map, is in the centre of the castle, but also about half way up or down. It also has ishigaki ramparts. Above there is a sort of square gate complex ruin as the entrance to bailey sixteen. Beneath the shukuruwa (main bailey) is a valley flanked on either side by a series of small baileys carved into the ridges like a set of parallel giant steps. Following their respective ridges, these strands of terraced baileys get larger the higher they climb, and to the left and right (going up) there are twelve on each side. Although there is less ishigaki to oggle here I nonetheless was impressed by this array of climbing baileys.

Koźutsumijō has a sattelite fortification called Iwakura Castle.


Castle Profile
English Name Kozutsumi Castle
Japanese Name 小堤城
Alternate Names 小堤城山城
Founder Nagahara Clan
Year Founded Late 15th Century
Castle Type Mountaintop
Castle Condition Ruins only
Historical Period Pre Edo Period
Artifacts Kuruwa, Ishigaki, &c.
Features trenches, stone walls
Visitor Information
Access Yasu Station on the Biwako Line; 45 minute walk to trailhead across the Ieto River; 30 minute hike; or, hike via the castle ruins from the northern valley.
Visitor Information 24/7 free; mountain
Time Required 180 minutes
Location Yasu, Shiga Prefecture
Coordinates 35° 3' 53.39" N, 136° 3' 24.88" E
Loading map...
Added to Jcastle 2022
Contributor ART
Admin Year Visited Viewer Contributed
Friends of JCastle
Jōkaku Hōrōki
Jōkaku Tanbō

(2 votes)
Add your comment
Jcastle.info welcomes all comments. If you do not want to be anonymous, register or log in. It is free.



16 months ago
Score 0++

So, this highly enjoyable but little-known gem of a yamajiro has finally been discovered by another JCastle fan. I’ve been telling the website owner, Eric, for years how amazing this mountaintop castle is. Well, it looks like you with / without him finally made it to this impressive castle ruin in Shiga.

In the notes about the castle that you have described accurately how the main bailey is tucked a bit down mountain, surrounded by higher and protective baileys, unlike the usual design for a yamajiro, which would have the main bailey at the highest point of the castle. This feature of having the main bailey lower down in the castle design is similar to some other Rokkaku castles that I have mentioned in one of my comments for Omi-Kitanosho Castle. Another feature of this castle, which predated but would find a familiar echo in Nobunaga’s Azuchi Castle layout, is the path / stairway up north side of the castle. I reckon Azuchi Castle has adopted this in its design of the main stairway going up the castle, mimicking Kozutsumishiroyama Castle. All these terraced baileys going up the mountain at Kozutsumishiroyama Castle are now planted with conifers.

You certainly need a map for this Kozutsumishiroyama Castle when visiting this castle (and most yamajiros), but based on your photos uploaded here, you have missed the bailey with the most ishigaki. That is marked Bailey 15 on your map.

For those who want to save a bit of time, you can catch a bus from Yasu Station to Kibogaoka Park. Once at the park, walk across the open fields until you hit one of the trails there. There will be signs indicating the way up to Kozutsumishiroyama Castle from the south side.


16 months ago
Score 0++
OK, you've both convinced me. I'll put it on the list for fall 2023. I'll research and document everything with dozens of pictures for future travelers ! :)


21 months ago
Score 0++
The name of this site is a gosh-darn mystery. Jōkaku Hōrōki goes with こつづみ (kotsuzumi) whilst others go with こづつみ (Kozutsumi). Confused the heck of me. I went with the latter because it was most commonly listed and because it looks like a mistake, which means, by the twisted rules of Japanese, it must be accurate. Of course, linguistic morphology normally applies to the second mora in double 'tsu (つつ)', but Kozutsumi inverses this.