Nanao Castle (Iwami)

I didn’t explore the whole site, I focused on reaching the inner compound. It was all very interesting. Trails are narrow and near drops at times but otherwise not difficult to ascend or descend. Steep in places. Great views! Note that Google Maps sends you to the wrong starting point – start from

History

It’s not known when the castle was first built, but it’s mentioned in documents from the mid to late fourteenth century, and may date from as early as 1192. It was initially the back-up defensive fortress for the Masuda clan. The clan, previously known as the Mikimoto, had moved to the Masuda area after the beginning of the Kamakura period (from 1192), having been awarded western Iwami for their support of Minamoto no Yoritomo. They built the fortified residence Miyake-Odoi at a strategic spot on the Masuda River and that became their main base. Nanao Castle, nearly a kilometre away on Mt Nanao on the opposite side of the river, faced Miyake-Odoi.

The Masuda were allied to the Ōuchi, but supported Sue Harutaka who led a successful uprising against Lord Ōuchi Yoshitaka in 1551. In 1555 Harutaka was defeated by Mōri Motonari, and the expansionist Mōri clan were allies of the Masuda’s old enemies the Yoshimi. In this context the 19th lord, Masuda Fujikane (1529-97), moved the main base to the castle, which he strengthened. In 1556 Kikkawa Motoharu and the Yoshimi invaded Iwami. The Masuda held out for six months in the castle, but eventually yielded, losing much of their land and becoming Mōri vassals. The castle was further expanded, and the Masuda fought in various campaigns for the Mōri. The 20th lord, Masuda Motoyoshi (1558-1640), moved the HQ back to Miyake-Odoi. The clan left Masuda after the Battle of Sekigahara, although reportedly Tokugawa Ieyasu had been impressed by Motoyoshi and would have allowed him to keep his lands. Motoyoshi, loyal to the Mōri whose lands were severely reduced after the battle, is said to have refused the offer. (Motoyoshi was honoured by being allowed to include “Moto” in his name, after Mōri Motonari. He’s also identified as Motonaga and Masunaga.) Both Nanao Castle and Miyake-Odoi were abandoned.

What is thought to have begun as a fairly small fortress was expanded till by the end of the century the entire mountain was fortified. The castle’s shape was like a Y, with the inner compound towards the end of the central stroke. There were about 40 kuruwa (baileys) as well as protective ridges and moats. Twenty kuruwa remain along with earthworks, dry moats and wells. Excavations have uncovered the wells and also the foundations of various buildings (buried again).

Nanao Castle and Miyake-Odoi have together been designated as a National Historic Site – the “Masuda clan fortification ruins”.

Field Notes

I didn’t explore the whole site, I focused on reaching the inner compound. It was all very interesting. Trails are narrow and near drops at times but otherwise not difficult to ascend or descend. Steep in places. Great views!

Note that Google Maps sends you to the wrong starting point – start from the ground level of Sumiyoshi Shrine. More than 100 steps to the upper level of the shrine, then the trail begins after that – about another 250-300m up to the inner compound. The site is well maintained with foliage cut back and some trees removed. There’s directional and some other signage. A map shows named structures or sub-sites which I must’ve passed or seen, such as the stable area and the “drum platform” but sorry to say I don’t know what they look like so I’m not sure if I captured them in any photos.

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Gallery

Inner compound
Inner compound
View from inner compound
Anime figure at the inner compound
Inner compound - just above the second level und
Another view from the inner compound
Inner compound
Inner compound, second level
Storehouse site
Inner compound, second level
Inner compound, second level
Looking up towards the inner compound
Trail to the Ryo no Demaru
Trail to the Ryo no Demaru and possible site of castle structure
Looking towards the route back down or to the Ryo no Demaru
The second section of the trail upwards
The first part of the trail from the shrine
Sumiyoshi Shrine, ground level
Steps down from Sumiyoshi Shrine, upper level
Sumiyoshi Shrine, upper level
Sumiyoshi Shrine, upper level
Showing the position of the inner compound on Mt Nanao - circled top right
Castle gate relocated to Ikō-ji
Castle gate relocated to Ikō-ji, looking outwards
Castle gate relocated to Ikō-ji
Castle gate relocated to Ikō-ji

Castle Profile
English Name	Nanao Castle (Iwami)
Japanese Name	石見七尾城
Alternate Names	Masuda Castle
Founder
Year Founded
Castle Type	Mountaintop
Castle Condition	No main keep but other buildings
Designations	National Historic Site
Historical Period	Pre Edo Period
Artifacts	One gate, relocated to Ikō-ji Temple
Features	gates, trenches
Visitor Information
Access	Open 24 hours
Hours	It's a 20 minute walk from Masuda Station. There may be bus stopping somewhere nearby, but the walk there is easy - flat.
Time Required	One hour
Location	Masuda, Shimane Prefecture
Coordinates	34.67224, 131.86256
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Admin
Added to Jcastle	2025
Contributor	AnneMcL
Admin Year Visited	Viewer Contributed

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