Kusunoki Castle Ruins (Kami-Akasaka Castle)
On a ridge that drops into deep valleys on three sides, roughly 350 meters above the southern Osaka village of Chihayaakasaka, lie the earthworks of a fortress that the fourteenth-century commander Kusunoki Masashige relied on as his clan's principal stronghold. The war chronicle Taiheiki and older local records call it Kusunoki Castle (Kusunoki-jo). Historians more often use the name Kami-Akasaka Castle, to keep it distinct from a second, lower fort nearby. The official designation joins both: Kusunoki Castle Ruins (Kami-Akasaka Castle).
The site has no keep, no stone ramparts of the kind later castles are known for, and no reconstructed buildings. What survives is the shape of the mountain itself, cut and flattened by hand. A chain of level terraces, ditches dug across the ridgeline, and a wide summit clearing from which, on a clear day, the towers of central Osaka stand out to the north.
The castle was never meant to stand alone. Across the foothills of Mount Kongo, Masashige and his allies raised a string of forts. Together with Chihaya Castle and the lower Akasaka fort, Kusunoki Castle formed a defensive network that, in 1333, helped bring down the Kamakura shogunate.
The Siege of 1333
In the autumn of 1331, Emperor Go-Daigo's plot to overthrow the Kamakura shogunate collapsed, and the emperor fled to Mount Kasagi. Kusunoki Masashige rose in support and fortified the hills of his home district of Kawachi. The first Akasaka fort, hastily built, fell within weeks, and Masashige withdrew. He returned to the area the following year and built anew. It was during this second campaign that the fortress on the Kami-Akasaka ridge took the form whose outline visitors trace today.
The decisive fighting came in the spring of 1333. The shogunate pushed a large army into Kawachi, and on the twenty-second day of the second month, 8 March by the modern calendar, it closed on Kami-Akasaka. Masashige did not command here in person. He had placed the castle under Hirano Shogen Nyudo, with his own younger brother Kusunoki Masasue as second-in-command, while he directed the wider defense from Chihaya Castle higher in the mountains.
The choice of Hirano is itself telling. He was a noted akuto, one of the unruly provincial fighters who had defied shogunal authority in the decades before the war, and he held a court rank above Masashige's own. The shogunate treated Kami-Akasaka as a main objective rather than a sideshow, assigning Aso Harutoki, commander of its Kawachi-route force, to the assault.
Hirano's garrison held for about ten days. According to the Taiheiki, the defenders were undone not in battle but by thirst: the besiegers found the channel that carried water up to the castle and cut it. Whether the supply was severed exactly as the chronicle describes is uncertain, yet the account has shaped the site's memory ever since. Hirano surrendered with a small band of men around the first day of the intercalary second month, 17 March 1333. Masasue slipped away to Chihaya. The Taiheiki records that Hirano was later executed at Rokujo-gawara in Kyoto.
Kami-Akasaka fell, but the campaign did not. Chihaya Castle held through a long siege, the shogunate's grip loosened, and within months the Kamakura regime was gone. The fortress kept its military role afterward, serving as a southern stronghold during the wars between the Northern and Southern Courts until it passed to the northern side in 1360.
A Historic Site Since 1934
On 13 March 1934, Kusunoki Castle Ruins entered the national register of Historic Sites, together with Chihaya Castle and the lower Akasaka fort. Two months later, Chihayaakasaka Village was named the body responsible for the site's care. The official survey assigns the ground to the category covering castle ruins and other places bound up with political history. Its older description praised the position: a peak standing apart, cliffs and ravines on three sides, a commanding view, a natural fortress. The same record notes a valley behind the castle where a spring still gathered water, remembered as the source that once supplied the garrison.
What gives the site its standing is less any single structure than the link between ground and event. The terraces and ditches are physical evidence of the kind of mountain warfare that made Masashige's name, a small force fighting from prepared high ground against a far larger one. The three castles designated together in 1934 are usually read as a set, and Kami-Akasaka is the one where the surviving earthworks are clearest.
Walking the Ruins
The climb begins near the lower gate, where an information board marks the spot known as Ichi-no-kido, the first of the castle's gates. From here the path runs through a kiridoshi, a corridor cut down into the slope so that anyone moving along it is hemmed in on both sides. The approach itself was made to serve as a defense.
Past the second and third gate positions the trail reaches Soroban-bashi, the abacus bridge. Today the way is continuous, but the name and the ground point to a horikiri, a ditch cut straight across the ridge, once spanned by a removable wooden bridge. Beyond it lies Chawanbara, a level terrace whose name, roughly "bowl field," comes from the pottery shards turned up there. The finds confirm that the spot served as a kuruwa, one of the flattened enclosures that make up a Japanese mountain castle.
The path ends at the summit clearing called Senjojiki, broad enough that its name claims a thousand tatami mats. A belt enclosure, the obi-kuruwa, wraps the high ground. The view runs north across the Osaka plain to the city. The logic of the site becomes plain on arrival. Anyone holding this ground sees an enemy long before the enemy arrives, and the slopes do much of the defending.
Look closely at those slopes and you will find ditches that do not belong to the fourteenth century. Long moats following the contour of the hill, and a cluster of parallel dry trenches, are the work of later builders. Excavation has recovered objects spanning the fourteenth to sixteenth centuries, and the contour moats are thought to date from the Warring States period, when the fort was repaired and used again during the conflicts surrounding the Hatakeyama clan. The castle visitors walk today is layered: a fourteenth-century battlefield reshaped by later hands.
Around the Castle
Chihayaakasaka is the only village in Osaka Prefecture, and it treats Masashige as its own. A short distance from the castle stands the place traditionally held to be his birthplace, near a well said to have provided the water for his first bath. The village folk museum nearby gathers documents and excavated material connected with the Kusunoki family and the castles.
The natural base for a visit is Michi-no-Eki Chihayaakasaka, a roadside station small enough to be called the cutest in Japan and the oldest such station in the prefecture. Its shop sells produce grown on the local terraced fields, and its second-floor cafe serves dishes built around village rice and vegetables, including a curry plated to resemble the terraces themselves.
Other reminders of Masashige stand within easy reach. The Hoken-to, a tall stone tower, was raised in 1940 to mark six centuries since his death, and the slope below it fills with daffodils in late winter. Chihaya Castle, where Masashige held out through the siege of 1333, is now the grounds of Chihaya Shrine. The lower Akasaka fort sits above the Shimo-Akasaka terraced rice fields, themselves counted among the finest in the country. For walkers, the castle ridge is also a station on routes climbing Mount Kongo, the 1,125-meter peak that rises behind the village.
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Q&A
- How long does it take to reach the summit?
- The walk from the parking area near the first gate to the summit clearing takes about twenty minutes. It is a mountain trail with a steady climb, so sturdy shoes are sensible. Allow extra time in hot weather, when the ascent is genuinely sweaty work.
- There are no castle buildings, so is there anything to see?
- There is no keep and no reconstruction. The interest lies in the earthwork itself: the cut-down approach corridor, the ditch at Soroban-bashi, the terraces, and the contour moats added in later centuries. For anyone curious about how a medieval mountain castle actually used terrain, the site reads more clearly than many places with rebuilt towers.
- Can I get there by public transport?
- The bus network serving the village was reorganized after the previous operator ended service in late 2023, and routes now run as a community bus system. Connections from Tondabayashi Station on the Kintetsu line are possible but infrequent, and the castle still lies a walk of around half an hour from the nearest stop. Travelers without a car should check current timetables in advance; many visitors come by car and use the roadside station's parking.
- When is the best time to visit?
- Late autumn and winter give the clearest long views from the summit, and the daffodils below the Hoken-to bloom from late winter. Spring brings cherry blossom to the village. Summer is humid and the climb hard going. The trail has little shade, so sun protection matters in the warmer months.
- What is the difference between Kusunoki Castle, Kami-Akasaka, and the other Akasaka fort?
- All three names attach to Kusunoki fortifications in the same village. "Kusunoki Castle" is the old name for the fort on the Kami-Akasaka ridge, the subject of this article and the clan's main base. The lower Akasaka fort, Shimo-Akasaka, is a separate site on lower ground. The official Historic Site designation uses both names together, Kusunoki Castle Ruins with Kami-Akasaka Castle in parentheses, precisely to keep the two Akasaka forts distinct.
Basic Information
| Name | Kusunoki Castle Ruins (Kami-Akasaka Castle) / Kusunoki-jo Ato (Kami-Akasaka-jo Ato) |
|---|---|
| Location | Kiriyama, Chihayaakasaka, Minamikawachi District, Osaka Prefecture |
| Designation | National Historic Site |
| Date of designation | 13 March 1934 |
| Managing body | Chihayaakasaka Village |
| Period | Late Kamakura to Nanboku-cho period (14th century), with later modification |
| Other names | Kusunoki Castle, Onenda Castle, Kiriyama Castle |
| Access | About a 20-minute climb from the trailhead parking; mountain path |
| Admission | Free; open site |
| Note | No buildings remain; earthworks only |
References
- Cultural Heritage Online, "Kusunoki Castle Ruins (Kami-Akasaka Castle)"
- https://bunka.nii.ac.jp/heritages/detail/216909
- Database of National Cultural Properties, Agency for Cultural Affairs
- https://kunishitei.bunka.go.jp/bsys/maindetails/401/1779
- Chihayaakasaka Village, "Exploring History"
- https://www.vill.chihayaakasaka.osaka.jp/kanko/rekishi/index.html
- Chiaka Portal, "Kami-Akasaka Castle Ruins"
- https://chiaka-portal.com/History/Remains/Kamiakasaka/kamiakasaka.htm
- Wikipedia, "Battle of Kami-Akasaka Castle" (Japanese)
- https://ja.wikipedia.org/wiki/上赤坂城の戦い
Last verified: 2026.05.26