Hirune Castle (Kagawa Prefecture) Complete Guide | A Thorough Explanation of the History and Highlights of the Impregnable Sanuki Mountain Castle
What is Hirune Castle?
Hirune Castle (Hirune-jo) is a medieval mountain castle located in the Maeyama district of Tawa, Sanuki City, Kagawa Prefecture. Built on the summit of Mt. Hirune (approximately 460 meters above sea level, with a relative height of approximately 220 meters), this castle was an impregnable fortress, said to have been named after the legend that “even if you took a nap, the enemy could not capture it.”
Currently, it is protected as a Sanuki City designated historical site, and the remains such as earthworks and moats are well preserved. As the base of the Kagawa clan, who ruled the eastern part of Sanuki Province (Eastern Sanuki), it was a central figure in regional control, with Hikita Castle and Toramaru Castle as its subsidiary castles.
History of Hirune Castle
Construction and the Rise of the Kagawa Clan
Hirune Castle is believed to have been built during the Kakitsu era (1441-1444). While there are various theories about the builder, it is generally believed to have been constructed by Kagawa Mitsuharu (or Kagawa Mitsuharu).
The Kagawa clan is said to be descended from Onnao Chitsugu, a descendant of the Sanuki no Kuni no Miyatsuko (provincial governor of Sanuki Province), and was a prominent family that had served as Kagawa County Magistrate for generations. From the late Heian period to the Kamakura period, they established themselves as a powerful local clan in this region.
Development in the Muromachi Period
In the Muromachi period, the Kagawa clan became the Jito (land steward) of Nagao Manor and expanded their power as vassals of the Hosokawa clan (later the Hosokawa clan). During this period, the Kagawa clan grew into a powerful daimyo in the eastern Sanuki region, controlling Ouchi County, Kagawa County, and even Shodoshima Island.
The Kagawa clan’s system of rule was structured around a three-castle system, with Hirune Castle as the main castle and Hikida Castle (Hikida Hanzan Castle) and Toramaru Castle as subsidiary castles. This arrangement allowed them to control key points on both maritime and land routes in the Seto Inland Sea, solidifying their regional control.
Turmoil of the Sengoku Period
With the arrival of the Sengoku period, Hirune Castle became embroiled in the power struggles within Sanuki Province.
Around Genki 1 (1570), relations with the Miyoshi clan of Awa Province deepened. In Genki 3 (1572), when the influence of Miyoshi Nagaharu of Awa extended to Sanuki, the head of the Kagawa clan, Kagawa Motomasa, moved to Hirune Castle, and Yasutomi Hizen-no-kami Morikata, a general on the Miyoshi side, was entrusted with the castle’s management.
During this period, the Chosokabe clan of Tosa Province had also begun their invasion of Sanuki Province, and the eastern Sanuki region was in a complex political situation. Hirune Castle, known as “the strongest castle in Shikoku” due to its formidable defenses, continued to function as a fortress that was difficult to conquer.
The Fall and Aftermath
While historical records are limited regarding the detailed circumstances of the castle’s fall, it is believed that the power of the Kagawa clan declined during Toyotomi Hideyoshi’s conquest of Shikoku in the Tensho era (1573-1592).
Ultimately, Hirune Castle was abandoned and remained unused during the Edo period, its remains lying dormant in the forest. Today, it is preserved as a local historical heritage site, attracting castle enthusiasts and history buffs.
The Layout and Structure of Hirune Castle
Location and Topography
Hirune Castle was built on the summit of a ridge branching off from Yahazuyama and Nyotaiyama, commonly known as “Hiruneyama” (Hirune Mountain). Located at an altitude of approximately 460 meters, with a relative height of about 220 meters from the base of the mountain, this location offered an excellent vantage point for observation and overlooking the surrounding area. However, it also presented a challenging climb for attackers, forcing them to ascend a steep slope.
This geographical advantage is believed to be the reason for the legend that “it could be conquered even while taking a nap.”
Main Enclosure (Honmaru)
The main enclosure is thought to be a fortified enclosure located on the eastern side of the mountaintop. This was the central area where the lord’s residence and command post were located. A earthen embankment remains on the southeast side of the main enclosure, allowing us to confirm traces of defensive structures.
The earthen embankment was a mound of earth designed to prevent enemy intrusion, and it functioned as a defensive position where soldiers could hide or fire arrows from behind. The clearly visible earthen embankment is a valuable relic that conveys the castle-building techniques of the time.
Western Enclosure
The tip of the ridge extending west from the main enclosure is slightly elevated, and the western enclosure is located there. This enclosure currently houses a shrine and is an object of local worship.
The western enclosure is thought to have served as a forward base, monitoring and defending against enemy incursions from the west.
Moats
Moats, an important defensive feature of mountain castles, have also been identified. A moat is a dry ditch artificially created by cutting through a ridge, functioning as an obstacle to hinder enemy advances.
The moats at Hirune Castle made it difficult for attackers to approach the castle along the ridge, and were an important element in enhancing the castle’s defenses.
Other Remains
Although relatively small in scale, multiple enclosures are arranged, characterized by an efficient use of the limited mountaintop area. Each enclosure is thought to have been used as a soldier’s garrison or a storage area for supplies.
Highlights of Hirune Castle
Well-Preserved Earthworks
The greatest highlight of Hirune Castle is the earthworks remaining on the southeast side of the main enclosure. These earthworks, still clearly visible after hundreds of years, are a valuable historical relic that conveys the castle-building techniques and defensive philosophies of the time.
By observing the height and shape of the earthworks, one can imagine how they defended against enemy attacks and the tactics used at the time.
The Impressive Moat
The moat cutting across the ridge is a defensive structure unique to mountain castles. Standing before the deeply excavated moat, one can truly appreciate the difficulty of siege warfare.
The scale and placement of the moat reveal how much importance the Kagawa clan placed on this castle and how they implemented strong defenses.
Views
From the mountaintop at an altitude of 460 meters, you can enjoy a panoramic view of the Higashi-Sanuki region. On a clear day, you can see as far as the Seto Inland Sea and Shodoshima Island, giving you a real sense of why the Samukawa clan chose this area as their base of operations.
Surrounding Historical Environment
Near Hirune Castle is Okubo-ji Temple, the final temple of the Shikoku 88 Temple Pilgrimage. This region, where the history of a medieval castle and the Shikoku pilgrimage intersect, offers a fascinating blend of multi-layered history.
Access and Visiting Guide to Hirune Castle
Location
Address: Tawa (Maeyama area), Sanuki City, Kagawa Prefecture
Access Methods
Access by Car:
- Approximately 30 minutes from Shido IC on the Takamatsu Expressway
- Take National Route 377 towards Tawa
- Parking available near the trailhead (limited number of spaces)
Public Transportation:
- Taking a taxi from Shido Station on the JR Kotoku Line is convenient
- Bus services are limited, so advance confirmation is necessary
Climbing Route
From the trailhead to the main enclosure at the summit, you will climb approximately 220 meters in elevation. The hiking trail is well-maintained, but there are steep sections characteristic of mountain castles, so the following preparations are recommended:
- Estimated time: Ascent: 40-60 minutes, Descent: 30-40 minutes
- Difficulty: Intermediate (for experienced hikers)
- Clothing: Comfortable clothing, trekking shoes
- Items to bring: Drinking water, towel, insect repellent (summer)
- Season: Spring and autumn are best; heat protection is essential in summer; be aware of snow in winter
Precautions when visiting
- Bears and wild animals: Be aware of wild animals such as bears and wild boars in the mountains. Carrying a bear bell is recommended.
- Avoid solo climbing: Visiting with multiple people is safer if possible.
- Check the weather: Visiting on a sunny day is recommended as it can be slippery and dangerous in rainy weather.
- Protect the ruins: Please be careful not to climb on or damage the ruins such as earthworks.
- Take your trash home: Please be sure to take your trash home to protect the historical site.
Related historical sites in the vicinity
Hikida Castle (Hikida Hanzan Castle)
Hikida Castle, which functioned as a branch castle of Hirune Castle, is known as a sea castle facing the Seto Inland Sea. It was a strategically important location controlling a key point for maritime traffic, and played an important role in the expansion of the Kagawa clan’s power.
Currently, it is selected as one of the “Continued Top 100 Japanese Castles,” and the remains such as stone walls are well preserved. Visiting it together with Hirune Castle will allow you to gain a deeper understanding of the Kagawa clan’s system of rule.
Hikida Castle, which functioned as a branch castle of Hirune Castle, is known as a sea castle facing the Seto Inland Sea. ### Toramaru Castle
Toramaru Castle, another subsidiary castle, also formed part of the defensive line in the eastern Sanuki region. Visiting all three castles allows you to experience the castle network of medieval Sanuki.
Amataki Castle
The eastern Sanuki region also contains other mountain castles related to the Samukawa clan and surrounding forces, such as Amataki Castle. Visiting them as part of a castle tour is highly recommended.
Okubo-ji Temple
Okubo-ji Temple, the 88th temple of the Shikoku 88 Temple Pilgrimage, is located near Hirune Castle. This temple, visited by many pilgrims as the final temple of the pilgrimage, tells the story of a history of faith that has continued since the Middle Ages.
Historical Significance of Hirune Castle
Center of Eastern Sanuki Rule
Hirune Castle was not merely a single mountain castle, but the base of the Samukawa clan, who ruled a vast area including Samukawa County, Ouchi County, and Shodoshima Island. The three-castle system of Hirune Castle, Hikita Castle, and Toramaru Castle is an important example of regional rule in medieval Sanuki.
The Strongest Fortress in Shikoku
Its defensive capabilities, hailed as “the strongest fortress in Shikoku,” demonstrate the high level of castle-building technology that made maximum use of the terrain. Its steep location, with a relative elevation of 220 meters, and multi-layered defenses using moats and earthworks, provided an overwhelming advantage in siege warfare.
Traces of Sanuki Samurai
The Kagawa clan, descendants of the Sanuki provincial governor, was a prominent family with a long history dating back to ancient times. The history of the Kagawa clan, which developed from district officials to land stewards and then to Sengoku daimyo (feudal lords), represents a typical growth process of Sanuki samurai and is an important case study in regional history research.
Current Status and Challenges of Research on Hirune Castle
Excavation and Preservation
Hirune Castle is currently protected as a Sanuki City designated historical site, but full-scale excavation surveys are limited. Further academic research, such as detailed surveying of the remains and creation of layout maps, is desired.
Limitations of Historical Sources
Primary sources concerning the Samukawa clan and Hirune Castle are limited, leaving many questions unanswered, such as the castle’s construction date, changes in its lords, and the circumstances of its fall. Further historical excavations and comparative studies with surrounding castles are expected to shed light on a more detailed historical picture.
Utilization as a Tourism Resource
Despite its attractive characteristics as an impregnable mountain castle, Hirune Castle is not particularly well-known. Appropriate maintenance and information dissemination are expected to allow it to be utilized as a regional historical tourism resource.
Significance of Visiting Hirune Castle
Visiting Hirune Castle offers value beyond simply viewing castle ruins.
Climbing the steep mountain path and standing on the summit, one can truly grasp how medieval samurai viewed this land and why they built a castle here. The well-preserved earthworks and moats convey the technology and wisdom of people from hundreds of years ago.
The legend that “it wouldn’t fall even if you took a nap” not only signifies its impregnability, but also embodies the pride and confidence of those who defended this castle. Touching upon that spirit is a key part of the historical exploration.
On this quiet mountaintop surrounded by the mountains of Sanuki, the time spent contemplating the history of medieval Sanuki will be a precious experience that allows you to forget the hustle and bustle of modern life.
Summary
Hirune Castle is a masterpiece of medieval mountain castle construction remaining in Sanuki City, Kagawa Prefecture. Built by the Kagawa clan during the Kakitsu era, it served as the center of control for the eastern Sanuki region, known as “the strongest castle in Shikoku.”
The remains of earthworks and moats on the 460-meter-high mountaintop are valuable historical relics that convey the castle-building techniques of the time. The three-castle system formed with Hikita Castle and Toramaru Castle holds historical significance as a typical example of regional control in medieval Sanuki.
The climb, with its elevation difference of 220 meters, is by no means easy, but the view from the summit and the well-preserved ruins more than make up for the effort. This historical site is a must-visit for anyone interested in the history of Sanuki or a fan of mountain castles.
Visiting this site along with Okubo-ji Temple, the final stop on the Shikoku 88 Temple Pilgrimage, and its subsidiary castles, Hikida Castle and Toramaru Castle, will allow you to gain a deeper understanding of the medieval history of the eastern Sanuki region.
