Complete Guide to Tsurugatake Castle | History and Highlights of a Medieval Mountain Castle in Nankan-cho, Tamana-gun, Kumamoto Prefecture
What is Tsurugatake Castle?
Tsuzuratake Castle is a medieval mountain castle located in Kanto, Nankan-cho, Tamana-gun, Kumamoto Prefecture. Also known as Otsuyama Castle, Nankan Castle, Maizuru Castle, and Tsurugatake Castle, it played an important role as a strategic point in northern Higo Province. Built on the summit of Mt. Otsuyama, approximately 230 meters above sea level, the castle occupied a strategically crucial position near the border between Chikugo Province (present-day Fukuoka Prefecture) and Higo Province (present-day Kumamoto Prefecture).
Currently, it is maintained as Otsuyama Nature Park, and the remains such as baileys, stone walls, moats, and vertical trenches are well preserved. Although relatively unknown within Kumamoto Prefecture, this castle ruin is attracting attention from castle enthusiasts and history buffs as a valuable historical site that strongly retains the characteristics of a medieval mountain castle.
History of Sagake Castle
Construction and Development by the Otsuyama Clan
The exact construction date of Sagake Castle is unclear, but it is believed to have been built by the Otsuyama clan, who ruled this area from the Kamakura period to the Nanboku-cho period. The Otsuyama clan was a powerful local family in northern Higo Province, and they acted as a branch or vassal of the Kikuchi clan.
The Otsuyama clan used Sagake Castle as their base and controlled the surrounding area. The castle’s location near the border with Chikugo Province and overlooking the Nankan checkpoint made it an important strategic point controlling a key transportation hub. During this period, Higo Province was dominated by the rise of the Kikuchi clan, and it is presumed that the Otsuyama clan operated within their sphere of influence.
Changes in the Sengoku Period
With the arrival of the Sengoku period (Warring States period), the situation in Higo Province became complex. After the decline of the Kikuchi clan, powerful daimyo of Kyushu, such as the Otomo, Ryuzoji, and Shimazu clans, vied for control of Higo Province. It is believed that the lord of Sakugatake Castle changed hands several times during this period of turmoil.
According to records, the Ohara clan controlled this castle for a time. The Ohara clan was one of the local lords of Higo Province and expanded their power during the chaotic Sengoku period. However, in the Tensho era (1573-1592), the northern part of Higo Province was also engulfed in war as the Shimazu clan, aiming to unify Kyushu, advanced northward.
Sasa Clan Rule under the Toyotomi Regime
In 1587 (Tensho 15), Toyotomi Hideyoshi pacified Kyushu, and Higo Province was given to Sasa Narimasa. Sasa Narimasa was a samurai from Echizen Province who was entrusted with the entire province of Higo by Hideyoshi. However, resistance to land surveys and new policies led to a Higo provincial uprising.
It is believed that Sakugake Castle also came under the control of the Sasa clan, and that Sasa clan retainers were temporarily stationed there. However, Sasa Narimasa was held responsible for the uprising and ordered to commit seppuku (ritual suicide) in 1588. Although this period was short, the Sasa clan’s rule marked a significant turning point in the history of Sakugake Castle.
The Era of Kato Kiyomasa and the Abandonment of the Castle
After Sasa Narimasa’s downfall, the northern part of Higo Province became the territory of Kato Kiyomasa. Kato Kiyomasa established Kumamoto Castle as his residence and governed Higo Province, consolidating and reorganizing the castles within his territory.
Regarding Sakugatake Castle, it’s possible that a retainer of Kato Kiyomasa was temporarily stationed there. However, after the Battle of Sekigahara (1600), when the Kato clan established their rule over the province, many subsidiary castles became unnecessary. The Edo Shogunate’s “One Castle Per Province” decree (1615) also contributed to the abandonment of Sakugatake Castle.
After its abandonment, the castle ruins were left neglected, but remnants such as stone walls and moats were preserved, albeit partially buried in nature, and remain to this day.
Layout and Structure of Sakugatake Castle
Overall Layout and Utilization of Topography
Sakugatake Castle is a typical medieval mountain castle built on the ridge from the summit of Mt. Otsu. It employs a linear layout with multiple enclosures centered around the main enclosure at the summit.
The castle’s location cleverly utilizes the natural terrain, with steep slopes serving as natural defensive walls. The northern and eastern sides, in particular, are steep cliffs, making enemy intrusion difficult. Ridges extend to the south and west, and trenches and vertical moats were constructed to defend against attacks from these sides.
Main Enclosure and Enclosures
The main enclosure is built at the highest point of the mountaintop, measuring approximately 40 meters east-west and 30 meters north-south. Earthen ramparts surround the main enclosure, and traces of stone walls can be seen in some areas.
Several enclosures are arranged around the main enclosure. These enclosures served as defensive structures to protect the main enclosure, as well as military garrisons and storage areas for supplies. Each enclosure is separated by elevation changes, designed to prevent easy enemy access to the main enclosure.
Characteristics of the Stone Walls
The stone walls of Gakujo Castle are relatively well-preserved for a medieval mountain castle. The stonework is primarily done using the “nozurazumi” method, a simple construction where natural stones are piled up as they are. This exhibits medieval technical characteristics and differs from the cut-stone and fitted-stone joinery seen in later early modern castles.
Stone walls are positioned around the main enclosure and along the edges of important baileys, serving to enhance defensive capabilities and secure flat surfaces for the baileys. The stone used is primarily granite quarried locally.
Moats and Vertical Moats
A notable defensive feature of Gakujo Castle is its multiple moats and vertical moats. Moats are dry moats dug to cut across the ridgeline, serving as an important defensive line to prevent enemy intrusion.
At least three moats have been identified at the castle site, particularly concentrated along the southern ridgeline. This indicates that attacks from the south were the most feared. The moats still retain a depth of approximately 2-3 meters, demonstrating the high level of defensive awareness at the time.
Vertical moats are moats dug vertically along the slope, serving to prevent enemies from climbing the slope to attack. At Sakugake Castle, multiple vertical moats are constructed on the slopes surrounding the main enclosure, creating a structure designed to withstand attacks from all directions.
Highlights of Sakugake Castle
View from the Main Enclosure
One of the greatest highlights of Sakugake Castle is the view from the main enclosure. Located on a mountaintop approximately 230 meters above sea level, the main enclosure offers panoramic views of the town of Nankan in Tamana District, and on clear days, even the Chikugo Plain and the Ariake Sea.
This view is not only aesthetically pleasing but also crucial for understanding the castle’s military function. The castle lord and soldiers at the time monitored surrounding movements from this position, quickly detecting enemy approaches. The unobstructed view towards the border with Chikugo Province clearly demonstrates its role as a border guard base.
Well-Preserved Moat Remains
Castle enthusiasts visiting Sakugake Castle are always drawn to the well-preserved remains of the moats. The moat on the southern ridge, in particular, retains ample depth and width, making it a valuable historical site that allows us to truly appreciate the defensive system of a medieval mountain castle.
Standing at the bottom of the moat, the towering cliffs (moat walls) on both sides create a sense of imposing presence as a defensive structure. The vertical moats extending from the moat can also be observed, showcasing the ingenuity of slope defense. These remains have largely untouched by later alterations, preserving much of their original appearance.
Remaining Stone Walls
The stone walls remaining around the main enclosure are also an important point of interest. While only a limited portion remains completely intact, several sections of rough-hewn stone walls can be seen, offering insights into medieval stonework techniques.
The stone wall on the east side of the main enclosure is particularly well-preserved, with approximately 1.5 meters of stonework remaining. The skillful combination of natural stones demonstrates the skill and ingenuity of the stonemasons. While some sections have collapsed, this also adds to the charm of a castle ruin with a long history.
Arrangement of the Enclosures
The arrangement of multiple enclosures is one of the charms of Gakugake Castle. Descending from the main enclosure, you can observe the enclosures arranged like terraced fields. The flat surfaces of each enclosure are relatively well-preserved, allowing you to imagine how the space was used in the past.
You can also observe the elevation differences between the enclosures and the locations of the entrances (koguchi), helping you understand the castle’s movement patterns and defensive strategies. In particular, the path from the second enclosure to the main enclosure shows a deliberate winding design, making it difficult to attack.
Harmony with the Natural Environment
Currently, the Gakugake Castle ruins are maintained as Otsuyama Nature Park, achieving a balance between the preservation of the castle ruins and the conservation of the natural environment. You can enjoy strolling through the castle ruins while appreciating the changing seasons: cherry blossoms in spring, fresh greenery in early summer, and autumn leaves in fall.
The stone walls and moats, quietly nestled within the forest, create a unique atmosphere where the romance of history and the beauty of nature merge. One of the biggest attractions of Gakutaku Castle is that you can enjoy exploring castle ruins and taking a nature walk at the same time.
Access Information
Access by Public Transportation
If you are visiting Gakutaku Castle by public transportation, it is convenient to use the Kyushu Shinkansen (bullet train). The nearest station is Shin-Ōmuta Station, and from there you can take a Sanko Bus.
It takes about 15 minutes from Shin-Ōmuta Station to the “Miyamae” bus stop, and then about 7 minutes on foot from the bus stop to the castle entrance. Since the number of buses is limited, it is recommended to check the timetable in advance. It is especially important to check the return bus schedule.
Alternatively, it is possible to access the castle by bus from Ōmuta Station on the JR Kagoshima Main Line, but since transfers may be necessary, using the Shinkansen is more convenient.
Access by Car
Access by car is the most convenient. It is easily accessible from the expressway, about 5 minutes from the Nankan Interchange on the Kyushu Expressway.
After exiting the Nankan Interchange, proceed along National Route 443 towards the town center of Nankan. Following the signs will lead you to the entrance of Otsuyama Nature Park. There is a free parking lot within the park. The castle entrance is just a few minutes’ walk from the parking lot.
If using a car navigation system, searching for “Otsuyama Nature Park” or “Kumamoto Prefecture, Tamana District, Nankan Town, Kanto” is recommended.
Parking Information
Otsuyama Nature Park has a free parking lot. It can accommodate approximately 20 cars and is usually not crowded, but during cherry blossom season and autumn foliage season, many tourists visit, so early arrival is recommended.
There are also restrooms in the parking lot, which is convenient for preparing before exploring the castle ruins. However, vending machines are limited, so it is recommended to prepare drinks and other necessities in advance.
Precautions When Visiting the Castle
Gakugake Castle is a mountain castle, and a certain level of physical fitness is required for the climb. The hike from the parking lot to the main keep takes approximately 20-30 minutes. While the walking trail is well-maintained, there are steep slopes and stairs, so comfortable clothing and broken-in shoes are recommended.
Particular caution is needed during and after rain, as the ground can become slippery. Also, remember to bring insect repellent in the summer and warm clothing in the winter.
Nearby Tourist Attractions
Historical Sites in Nankan Town
Nankan Town, where Sakugake Castle is located, has other historical sites. The Nankan Tea House Ruins were a resting facility used during the Edo period’s sankin-kotai (alternate attendance) system, and are now a park.
Nankan Town also retains its old townscape, allowing visitors to enjoy a stroll through the town in conjunction with exploring the castle ruins. The local history museum offers exhibits on the history of Nankan Town and Sakugake Castle.
Tamana Onsen
Approximately 20 minutes by car from Sakugatake Castle lies Tamana Onsen, one of Kumamoto Prefecture’s leading hot spring resorts. This ancient hot spring boasts a history of over 1300 years and is said to have fatigue-relieving and skin-beautifying effects.
It’s a great way to soothe your tired body after exploring the castle ruins. Tamana Onsen also has several day-trip bathing facilities, making it easy to enjoy the hot springs.
Castle Ruins in Northern Kumamoto Prefecture
For castle enthusiasts, we recommend visiting other castle ruins in northern Kumamoto Prefecture. Within a 30-minute drive, you can find Kikuchi Castle Ruins, Kumabe Clan Residence Ruins, and others, allowing you to experience the medieval history of northern Higo Province.
Furthermore, a short trip will take you to Kumamoto Castle (approximately 1 hour by car), one of Kumamoto Prefecture’s most famous castles. Comparing medieval mountain castles like Sakugatake Castle with early modern castles like Kumamoto Castle allows you to understand the development process of castles.
Cultural Value of Gakugake Castle
A Typical Example of a Medieval Mountain Castle
Gakugake Castle holds significant academic value as a typical example of a medieval mountain castle in the Kyushu region. Basic elements of medieval mountain castles, such as moats, vertical trenches, baileys, and stone walls, are well-preserved, making it a valuable resource for studying the castle-building techniques and defensive philosophies of the time.
In particular, as a castle of a local lord in northern Higo Province, it occupies an important position in regional history research. As a base of operations for local powerful families, including the Otsuyama clan, it provides clues to understanding the political and military situation of medieval Higo Province.
Excellent State of Preservation
A major characteristic of Gakugake Castle is that it has suffered almost no development in later periods. After its abandonment, it was left as a forest, which ultimately contributed to the preservation of its remains. Even in modern times, it was not targeted for housing development or agricultural land reclamation, so it retains much of its original appearance.
Such a well-preserved medieval mountain castle is rare nationwide, and its future preservation and utilization are highly anticipated. The local Nankan Town also recognizes its value as a cultural property and is striving for appropriate preservation and management.
Local Historical Education Resource
Gakugake Castle is also utilized as a local historical education resource. Local elementary and junior high schools sometimes conduct castle ruins visits as part of their local history studies, providing children with a place to learn about local history.
Furthermore, with the development of the Otsuyama Nature Park, it has attracted not only history enthusiasts but also general tourists and hiking enthusiasts, functioning as a local tourist resource.
Points to Note When Visiting Gakugake Castle
Estimated Visiting Time
For a visit to Gakugake Castle, it’s best to allow approximately 1 to 1.5 hours for the standard course. Approximately 20-30 minutes to ascend from the parking lot to the main enclosure, 30 minutes to explore the area around the main enclosure, and 20 minutes to descend.
For those who want to carefully observe the ruins or enjoy taking photographs, we recommend allocating about two hours. If you also plan to enjoy exploring the surrounding nature, you should add even more time.
Best Seasons for Visiting
While Gakutaku Castle can be visited year-round, each season offers its own unique charm. Spring (late March to April) is beautiful with cherry blossoms, making it a great time to enjoy a stroll through the castle ruins while admiring the flowers. Early summer (May to June) is ideal for visiting the castle, with its beautiful fresh greenery and mild weather.
Autumn (November) offers stunning autumn foliage, allowing you to fully appreciate both history and nature. Winter (December to February) makes the ruins easier to observe as the leaves have fallen, but warm clothing is necessary.
Summer (July to August) is characterized by dense greenery and numerous insects, making insect repellent and heatstroke prevention essential. Visiting during the cooler hours of early morning or evening is recommended.
Useful Items to Bring
The following items are useful to bring when exploring the castle ruins:
- Comfortable walking shoes (trekking shoes or sneakers)
- Drinks (especially plenty in summer)
- Towel
- Insect repellent spray (spring to autumn)
- Camera (for photographing ruins and scenery)
- Map or guidebook
- Rain gear (for unpredictable weather)
- Binoculars (for enjoying the view)
Also, having some basic knowledge about castles will deepen your understanding of the ruins. Learning a little about medieval mountain castles beforehand will make your visit more fulfilling.
Summary
Gakutake Castle is a medieval mountain castle located in Nankan-cho, Tamana-gun, Kumamoto Prefecture. It was built by the Otsuyama clan and has a history of changing lords, including the Ohara, Sasa, and Kato clans. Built on the summit of Mt. Otsuyama, approximately 230 meters above sea level, this castle boasts well-preserved remains such as baileys, stone walls, moats, and vertical trenches, making it a valuable historical site for learning about the structure of medieval mountain castles.
Its excellent accessibility, just a 5-minute drive from the Nankan Interchange on the Kyushu Expressway, is also a major draw. Because it’s developed as Otsuyama Nature Park, it’s popular not only with history buffs but also with nature walkers. The view from the main enclosure is magnificent, clearly demonstrating its role as a strategic point protecting the border between Higo and Chikugo provinces.
While Kumamoto Prefecture has many famous castle ruins, including Kumamoto Castle, local medieval mountain castles like Gakujo Castle possess their own unique charm and historical value. It’s a hidden gem that castle enthusiasts from all over Japan should definitely visit. Why not experience the history of northern Higo Province and feel the spirit of the Middle Ages at Gakujo Castle?
