Mōri Clan Castle Ruins: Tajihi Sarugake Castle and Kōriyama Castle
Tucked into the gentle hills of Akitakata City in Hiroshima Prefecture lie two castle ruins that together tell the story of one of the most remarkable rises to power in Japanese history. The Mōri Clan Castle Ruins—comprising the Tajihi Sarugake Castle Ruins and the Kōriyama Castle Ruins—were the cradle and stronghold of Mōri Motonari (1497–1571), the warlord who rose from a minor local lord to become the sovereign of nearly all of western Japan. Today, these forested mountainsides preserve hundreds of earthen terraces, dry moats, ridge-cuts, and pathways that hint at the scale of one of the largest mountain castles ever built in Japan.
For visitors who appreciate the quiet poetry of ruins, the chance to walk where a legendary strategist once lived, and the layered beauty of a forested mountain landscape, this site offers an unforgettable journey into the world of Japan's Sengoku period (1467–1615).
A Brief History of the Site
The Mōri family settled in Yoshida, in what was then Aki Province, during the 14th century, having been granted the local stewardship by the Kamakura shogunate. Over the following two centuries, the Mōri gradually built up a small fortification on the southeastern ridge of Mount Kōriyama, the natural foothold that would one day become the heart of their power.
Tajihi Sarugake Castle: The Childhood Home of Mōri Motonari
In the year 1500, Mōri Hiromoto handed leadership of the clan to his eldest son Okimoto and retired to a satellite fortress some four kilometers northwest of Kōriyama. With him came his four-year-old second son, Matsujumaru—the future Mōri Motonari. This was Tajihi Sarugake Castle. Motonari spent the formative years of his life here, weathering the early loss of both parents and the political turbulence that surrounded him, until at age 27 he returned to Kōriyama to succeed as head of the main Mōri line.
The castle was no mere retirement villa. Positioned overlooking a junction of roads from the Mido and Haji directions, with views back to Kōriyama, it served as the western shield of the Mōri territory against the powerful Takahashi clan to the north. It is also the birthplace of Motonari's eldest son Takamoto and his daughter Goryū-no-Tsubone, who would later marry into the Shishido family and help cement an alliance vital to the Mōri cause.
Kōriyama Castle: From Ridge Fortress to Mountain Stronghold
When Motonari assumed the headship in 1523, Kōriyama Castle was still a modest hill fort. Under his leadership, however, the entire mountain—standing about 400 meters above sea level, with a relative height of roughly 200 meters—was gradually transformed into a vast military complex. By the late Sengoku period, the castle covered an area approximately 1.1 kilometers east-west and 0.9 kilometers north-south, with more than 270 leveled terraces (kuruwa) radiating from the central keep along the mountain's natural ridges. Temples, residences, and storehouses were arranged inside the fortifications, while a planned town with markets at its base served as the political and economic engine of the Mōri domain.
The castle's most famous moment came in the winter of 1540–1541, when Motonari, with only a few thousand defenders—some of them farmers, women, and children gathered into the fortress—withstood a siege by an Amago army said to number 30,000. Through clever ambushes, careful use of terrain, and the timely arrival of Ōuchi reinforcements, the Mōri turned what seemed certain destruction into a decisive victory. This battle, known as the Battle of Yoshida-Kōriyama, propelled Motonari onto the regional stage and is remembered as one of the great defensive triumphs of the Sengoku period.
By the time of Motonari's grandson, Mōri Terumoto, the castle had been further modernized with stone walls and tiled roofs. In 1591, however, Terumoto moved his headquarters to the newly built Hiroshima Castle in the coastal plain, and Kōriyama gradually faded from active use, eventually being abandoned around the turn of the 17th century.
Why It Was Designated a National Historic Site
Kōriyama Castle was designated a National Historic Site in 1940, in recognition of its outstanding scale, exceptional state of preservation, and pivotal role in the history of the Sengoku period. In 1988, Tajihi Sarugake Castle was added to the designation, and the combined site was renamed "Mōri Clan Castle Ruins: Tajihi Sarugake Castle Ruins and Kōriyama Castle Ruins." Together they form an unusually complete record of how a regional warrior family rose, expanded, and adapted its fortifications across two centuries.
Three qualities give the site its national importance. First, the sheer scale and complexity of Kōriyama Castle—one of the largest mountain castles in western Japan—offers a rare physical record of a transitional fortress that fused traditional yamashiro (mountain castle) design with the more residential, administrative character of later early-modern castles. Second, the close pairing of Tajihi Sarugake and Kōriyama allows visitors and scholars to trace, in a single landscape, the entire arc of Motonari's life: childhood, accession, defense, expansion, and death. Third, the surviving earthworks—massive ridge-cuts (horikiri), terraces, and pathways—remain remarkably legible after centuries of forest growth, making the site an invaluable resource for understanding the engineering of Japanese mountain castles.
Highlights and Things to See
The Honmaru and Central Keep of Kōriyama
The summit of Mount Kōriyama, where the honmaru (main bailey) once stood, is reached by a steady climb of roughly 45 minutes from the base. While no buildings remain, scattered foundation stones and the outline of the watchtower platform speak quietly of the strategist who once gazed down from here over the Yoshida basin. The surrounding terraces—Sandan-no-Dan, Anigaki-no-Dan, and others—form a spiral of leveled platforms that gives a vivid sense of the original layout.
The Tomb of Mōri Motonari and the Hyakuman Isshin Monument
Halfway up the mountain stands the tomb of Mōri Motonari, beautifully framed by ancient cedars and a deep carpet of moss. Nearby is the Hyakuman Isshin (literally "a million people, one heart") monument, inscribed with the philosophy of unity Motonari is said to have imparted to his three sons—a teaching now familiar in Japan as the "Three Arrows" parable. Many visitors find this part of the climb the most atmospheric and moving.
The Massive Ridge-Cuts of Tajihi Sarugake Castle
At Tajihi Sarugake, the southern face of the main bailey preserves a series of enormous horikiri—ridge-cuts dug to sever the natural spine of the mountain and prevent attackers from advancing along it. The depth and width of these cuts is striking, and they are widely regarded as essential viewing for anyone interested in the engineering of Sengoku-period mountain castles. The site is divided into four zones: the summit lookout (Monomi-maru), the central bailey group, a mid-slope monastery district, and the demaru (outer fort) on the plain below.
Kiyomi Shrine and the Castle Town
At the southern foot of Kōriyama stands Kiyomi Shrine (Suga Jinja), the spiritual heart of the Mōri family. Its rōfuda tablets bear the names of generations of Mōri lords, and its role as the family's prayer site stretches back centuries before the castle's expansion. The surrounding streets still trace the layout of the original castle town, with names like Mikkaichi, Muikaichi, and Tōkaichi recalling the markets that once thrived here.
Visitor Information and Surrounding Attractions
The most popular starting point for exploration is the Akitakata City Museum of History and Folklore, located at the southern foot of Kōriyama. Here visitors can examine a detailed scale model of the castle, view artifacts and documents related to Mōri Motonari, and pick up an English-friendly map of the trails. The museum is also the official stamp location for those collecting stamps from Japan's "100 Famous Castles."
The full circuit of Kōriyama can take anywhere from two to four hours depending on how thoroughly one wishes to explore. Sturdy walking shoes, water, and a hat are strongly recommended. Trails are well marked, but the terrain is uneven and the climb is steady. Tajihi Sarugake Castle, by contrast, is a more demanding hike, with steep slopes and limited signage; it is best attempted by those with hiking experience and ideally with a local guide.
Nearby attractions include the Suzuo Castle Ruins (birthplace of Motonari, according to one tradition), the road station Michi-no-Eki Mitsuya-no-Sato Akitakata, and the tombs of Mōri Hiromoto and his wife near the foot of Tajihi Sarugake. Guided tours, organized by knowledgeable local volunteers, are highly recommended for those who want to make the most of a visit.
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Q&A
- Who was Mōri Motonari, and why does he matter?
- Mōri Motonari (1497–1571) was a Sengoku-period warlord who, in a single lifetime, transformed his small clan into the dominant power of western Japan, ruling ten provinces. He is celebrated for his diplomatic skill, his strategic brilliance, and the famous parable of the "Three Arrows," in which he is said to have taught his three sons that unity makes a family unbreakable.
- How long does it take to walk Kōriyama Castle?
- The official guide suggests about 45 minutes from the museum to the main bailey, but most visitors should plan for two to four hours to enjoy the side trails, the tombs, and the views. Visitors aiming to see every kuruwa, including the older eastern bailey, may want to allow half a day.
- Are there any buildings or castle structures still standing?
- No original buildings remain. Visitors will find earthworks—leveled terraces, ridge-cuts, foundation stones, and well sites—rather than reconstructed walls or keeps. The atmosphere is one of a forested archaeological site, and a model at the Akitakata City Museum of History and Folklore helps visitors visualize what once stood here.
- Is the site accessible without a car?
- Yes. From Hiroshima Bus Center, take a bus bound for Yoshida (approximately 90 minutes) and alight at the Akitakata City Hall stop. The museum and the Kōriyama trailhead are within a short walk. Tajihi Sarugake Castle is more remote and is better reached by car or taxi.
- When is the best season to visit?
- Spring and autumn are particularly rewarding. In spring, the cherry blossoms around the foot of the mountain frame the climb beautifully; in autumn, the maples and other deciduous trees turn the trails into a tunnel of color. Summer can be hot and humid, while winter occasionally brings light snow that lends the ruins a quiet, contemplative atmosphere.
Basic Information
| Name | Mōri Clan Castle Ruins: Tajihi Sarugake Castle Ruins and Kōriyama Castle Ruins |
|---|---|
| Location | Yoshida-chō, Akitakata, Hiroshima Prefecture |
| Designation | National Historic Site (Kōriyama Castle designated in 1940; expanded in 1988 to include Tajihi Sarugake Castle and renamed to the current title) |
| Period | Mainly 14th to late 16th centuries (Mōri clan headquarters until 1591) |
| Site Scale | Kōriyama Castle: approx. 1.1 km east-west, 0.9 km north-south; over 270 terraces. Tajihi Sarugake Castle: four major zones from summit lookout to lowland outer fort |
| Admission | Castle ruins: free of charge. Akitakata City Museum of History and Folklore: separate admission fee |
| Access | Approximately 90 minutes by bus from Hiroshima Bus Center to Akitakata City Hall stop, then a short walk to the museum and trailhead. By car: about 15–20 minutes from the Takata IC of the Chūgoku Expressway |
| Recommended Visit | 2–4 hours for Kōriyama Castle; allow additional time for the museum and Tajihi Sarugake Castle |
References
- Cultural Heritage Online: Mōri Clan Castle Ruins, Tajihi Sarugake Castle Ruins, Kōriyama Castle Ruins
- https://bunka.nii.ac.jp/heritages/detail/206293
- Akitakata City Official Site: Kōriyama Castle Ruins
- https://www.akitakata.jp/ja/shisei/section/kyouiku/shisekibunkazai/cultural_asset/siseki_kuni/mourisisiroato/kouriyamajyouato/
- Akitakata City Official Site: Tajihi Sarugake Castle Ruins
- https://www.akitakata.jp/ja/shisei/section/kyouiku/shisekibunkazai/cultural_asset/siseki_kuni/mourisisiroato/sarukakejyouseki/
- Akitakata Tourism Navi: Mōri Motonari and Kōriyama Castle
- https://akitakata-kankou.jp/main/motonari/
- Hiroshima Prefecture Board of Education: Tajihi Sarugake Castle Ruins
- https://www.pref.hiroshima.lg.jp/site/bunkazai/bunkazai-data-106120051.html
- Wikipedia: Yoshida-Kōriyama Castle
- https://ja.wikipedia.org/wiki/吉田郡山城
- Wikipedia: Tajihi Sarugake Castle
- https://ja.wikipedia.org/wiki/多治比猿掛城
Last verified: 2026.05.04