Complete Guide to Sanuki Castle (Futtsu City, Chiba Prefecture) | History, Highlights, and Access Explained
Located in Sanuki, Futtsu City, Chiba Prefecture, Sanuki Castle is a historically significant castle that existed for over 400 years, from the mid-Muromachi period to the Meiji Restoration. Also known as “Kamejo” (Turtle Castle), this castle, situated at a strategic point overlooking the Uraga Channel, was the site of fierce battles between the Mariya Takeda, Satomi, and Hojo clans during the Sengoku period. During the Edo period, it served as the political and military center of the Sanuki Domain.
This article comprehensively explains everything you need to know before visiting, including the detailed history of Sanuki Castle, its structural features, existing remains, the charm of the castle town, and access methods.
Overview and Location of Sanuki Castle
Sanuki Castle is a flatland castle built on a hill approximately 40 meters above sea level in the inland area of Futtsu City, Chiba Prefecture. Many people associate Futtsu City with the inner Boso coast facing Tokyo Bay, but Sanuki Castle is located in the central part of the city, built on a strategically important site at the entrance to the mountain path leading to Mount Kano.
The castle’s location on a hill overlooking the Obitsu River basin was a crucial point for monitoring and controlling the transportation routes connecting the inland and coastal areas of Kazusa Province. Furthermore, its geographical location across Tokyo Bay (Uraga Channel) from the Miura Peninsula made it a strategically important military stronghold on the Boso Peninsula.
The current site of Sanuki Castle is located at 884 Kitashinjuku, Kamezawa, Futtsu City, and other locations, south of Sanuki Junior High School. It is near the Tateyama Expressway, and the castle entrance is along the Prefectural Road Obitsu-Sanuki Station Line.
History and Background of Sanuki Castle
Muromachi Period: Castle Construction and the Mariya Takeda Clan
There are several theories regarding the construction date of Sanuki Castle, but the most prominent are that it was built during the Bun’an era (1444-1449) by the Nagao clan, who were chief retainers of the Kanto Kanrei Uesugi clan, and that it was first built by the Mariya Takeda clan in the mid-Muromachi period.
The Mariya Takeda clan was a branch of the Kai Takeda clan and a Sengoku daimyo who established their power in Kazusa Province. Sanuki Castle functioned as an important stronghold for the Mariya Takeda clan and played a central role in their control of Kazusa Province. While early records are unclear regarding the details of the castle’s lord, it is considered certain that the Mariya Takeda clan resided there.
Sengoku Period: The Struggle Between the Satomi and Hojo Clans
Entering the Tenbun era (1532-1554), the battles for supremacy over the Boso Peninsula intensified. The Satomi clan, based in Awa Province, defeated the Mariya Takeda clan and gained control of Sanuki Castle.
Particularly during the reigns of Satomi Yoshitaka and later Satomi Yoshihiro, Sanuki Castle served as the Satomi clan’s main stronghold. During this period, the Later Hojo clan, who controlled Sagami Province, attempted to expand into the Boso Peninsula, making Sanuki Castle the site of fierce battles between the Satomi and Hojo clans.
Due to its geographical location overlooking the Miura Peninsula across the Uraga Strait, the ownership of Sanuki Castle was critically important to both sides. The castle was repeatedly besieged and experienced a turbulent era with frequent changes in rulers. The battles during this period are recorded as important episodes in the Sengoku period history of the Boso Peninsula.
Edo Period: Establishment of the Sanuki Domain and its Government
In 1590, after Toyotomi Hideyoshi’s siege of Odawara, Tokugawa Ieyasu entered the Kanto region, and the area around Sanuki Castle came under Tokugawa control. During the Edo period, various daimyo were stationed at Sanuki Castle, and it became the administrative center of the Sanuki Domain.
Throughout the Edo period, the castle lords changed many times, but Sanuki Castle, despite being a small domain, continued to function as an important base in Kazusa Province. During the Edo period, Sanuki Castle transformed from a battlefield of fierce fighting during the Sengoku period to a center of administration and governance in a peaceful era.
Late Edo Period to Meiji Restoration: The Castle’s Demise
The Sanuki Domain existed until the end of the Edo period, but with the Meiji Restoration, it was abolished due to the abolition of the feudal domains and establishment of prefectures. In the early Meiji period, it lost its function as a castle, and many of its buildings were demolished.
Thus, Sanuki Castle, which existed for over 400 years from the mid-Muromachi period to the end of the Edo period, came to an end. Currently, it is preserved as a castle ruin, with remnants that evoke its former glory.
Structure and Layout of Sanuki Castle
Basic Structure of the Castle
Sanuki Castle was a flatland castle that skillfully utilized the hilly terrain, featuring a linear layout centered around the main keep, second bailey, and third bailey. The castle grounds extended approximately 400 meters east-west and 300 meters north-south, making it a valuable historical site illustrating the development of castles from the medieval to the early modern period.
The main keep was located at the highest elevation, surrounded by the second and third baileys fortified its defenses. Each bailey was demarcated by earthworks and dry moats, demonstrating various measures to prevent enemy intrusion.
The Only Stone-Walled Turret Base in Chiba Prefecture
The most distinctive feature of Sanuki Castle is that it is the only castle in Chiba Prefecture with a stone-walled turret base. While many castles in the Kanto region are made of earth, Sanuki Castle utilizes stone masonry techniques, which are believed to be the result of renovations during the Edo period.
The stone walls remaining near the main gate demonstrate the castle’s prestige and attest to the considerable wealth and technical skill of the Sanuki Domain during the Edo period. These stone walls are still well-preserved and are a valuable historical site that visitors can actually see.
Earthworks and Dry Moats
Within the castle grounds, earthworks and dry moats, characteristic of the Sengoku period, remain in excellent condition. In particular, the earthworks around the main keep reach heights of 3-5 meters in some places, demonstrating their function as defensive structures.
The dry moats separated the baileys and functioned as obstacles to hinder enemy advances. Even today, dry moats several meters deep can be seen, making them valuable teaching materials for learning about the structure of medieval castles.
Layout of the Enclosures
The third enclosure (San-no-maru) is currently a plaza with parking space for visitors. Climbing the slope from the entrance along the Prefectural Road Obitsu-Sanuki Station Line, you first arrive at the third enclosure.
From here, proceeding towards the main enclosure (Honmaru), you’ll find paths leading to the second enclosure (Nin-no-maru) and the main enclosure, allowing you to experience the layout and elevation differences of each enclosure firsthand. The passages between the enclosures are designed to be narrow, showcasing defensive ingenuity throughout.
Highlights and Remains of Sanuki Castle
Main Gate and Stone Walls
The first thing to note when visiting Sanuki Castle is the stone walls remaining near the main gate (Ote-guchi). You can observe rare stonework techniques in Chiba Prefecture up close and learn about castle construction techniques, such as stacking methods and stone selection.
Standing in front of the stone walls, you can still feel the grandeur of the Edo-period castle, making it a popular spot for photography.
Main Enclosure Site
From the highest point, the main enclosure site, you can enjoy panoramic views of the surrounding area. Imagining the castle tower and palace that once stood here, one can easily picture the castle lords surveying their territory from this vantage point.
The earthworks around the main enclosure are particularly well-preserved, making them valuable historical remains for studying the structure of medieval castles. In spring, cherry blossoms bloom, making it a spot where you can enjoy both historical walks and nature.
Dry Moats and Earthworks
The dry moats and earthworks remaining within the castle grounds are important historical remains that convey the defensive techniques of the Sengoku period. The dry moats separating the baileys are particularly deep, attesting to the high level of defense at the time.
There are also areas where you can walk on top of the earthworks, allowing for a three-dimensional understanding of the castle’s structure.
Archaeological Materials and Excavations
Excavations have been conducted at the Sanuki Castle site in the past, yielding archaeological materials such as ceramic fragments, roof tiles, and iron artifacts. These materials have been useful in determining the age of the castle and elucidating the lifestyle of the inhabitants, and some are stored and displayed at a facility in Futtsu City.
Archaeological excavations are revealing the castle’s transformation process and the layout of buildings from each era, and further research is expected.
The Charm of Sanuki Castle Town: From Edo to Showa – Towards a Future of Passing Down Stories
How to Enjoy a Stroll Through the Castle Town
The Sanuki district of Futtsu City is a valuable castle town where old buildings from the Edo period to the Showa period still remain. Futtsu City is promoting efforts to preserve and utilize this historical townscape under the concept of “From Edo to Showa – Towards a Future of Passing Down Stories,” as part of the “Futtsu City Picture Scroll: Sanuki Castle Town Stroll.”
Strolling through the castle town, you can enjoy the unique landscape where Edo-period merchant buildings and modern buildings from the Meiji, Taisho, and Showa periods coexist. By walking slowly and recalling the good old days, you can experience a feeling of stepping back in time.
The Historical Path to Mount Kanoyama
The castle town of Sanuki is also the starting point of the mountain path leading to Mount Kanoyama, a well-known recreational area. This path, used as a pilgrimage route during the Edo period, remains a popular route today, and exploring it in conjunction with Sanuki Castle offers a more enriching historical experience.
Along the path from the castle town towards Mount Kanoyama, you’ll find stone monuments and signposts that preserve the atmosphere of the past, making it an irresistible walking course for history buffs.
Traditional Buildings and Streetscapes
The Sanuki area is dotted with merchant houses and private residences dating from the Edo period to the early Showa period. Many of these buildings are still in use today, making them valuable living historical heritage.
By observing the exteriors, structures, and building materials used, you can learn about the architectural techniques and lifestyles of each era. Thanks to the cooperation of local residents, it’s sometimes possible to tour the interiors of some buildings, so we recommend checking Futtsu City’s tourist information before your visit.
Access and Visiting Information
Access by Car
Using the Tateyama Expressway
- Approximately 15 minutes from the Kisarazu Minami IC on the Tateyama Expressway
- Also accessible in approximately 20 minutes from the Kimitsu IC
Using General Roads
- From National Route 127, turn onto the Obitsu-Sanuki Station Prefectural Road and follow the signs.
Parking
- Parking spaces are available near the castle ruins entrance and in the San-no-maru area.
- Proceed east along the prefectural road south of Sanuki Junior High School; the entrance and parking area are located before the Tateyama Expressway overpass.
Access by Public Transportation
Using the JR Uchibo Line
- Get off at Sanuki-machi Station on the JR Uchibo Line, approximately 15-20 minutes on foot.
- Approximately 1.5 kilometers from the station to the castle ruins, a gentle uphill slope.
Route Bus
- Community buses operating within Futtsu City are available (please check operating days and times).
Notes for Visitors
- Because the castle ruins utilize the natural terrain, comfortable walking shoes are recommended.
- In summer, please remember to take precautions against insects; in winter, please take precautions against the cold.
- Be careful as the ground can be slippery in rainy weather.
- There are no lighting facilities within the castle ruins, so visiting before sunset is recommended.
- Please be sure to take your trash with you and take care not to damage the remains.
Estimated Visit Time
- Visiting only the castle ruins: Approximately 30-60 minutes
- Exploring the castle ruins and castle town: Approximately 2-3 hours
- Including thorough sightseeing and photography: Approximately half a day
Nearby Tourist Attractions
Kanoyama Mountain
Kanoyama Mountain, located about 20 minutes by car from Sanuki Castle, is a 379-meter-high mountain where you can enjoy spectacular views of Tokyo Bay and Mount Fuji from the summit. Kanoyama Jinnoji Temple is known as a place of ancient worship.
Futtsu Cape and Futtsu Park
Futtsu Cape, jutting out into Tokyo Bay, is a scenic spot offering panoramic views of Yokosuka and the Uraga Channel across the bay. Futtsu Park features an observation deck and a campsite, making it a popular spot for families.
Mother Farm
Located on the south side of Mt. Kano, Mother Farm is a tourist farm where visitors can enjoy interacting with animals and seasonal flowers. It can be combined with a visit to Sanuki Castle to create a family-friendly sightseeing plan.
Cultural Property Designation and Preservation Activities of Sanuki Castle
The Sanuki Castle ruins are recognized for their archaeological and historical value as castle remains from the medieval to early modern periods. Futtsu City is working to preserve and utilize the castle ruins, conducting regular grass cutting and preservation activities of the remains.
Local history enthusiasts and citizen volunteers are also actively involved in preservation activities, holding castle ruin tours and history lectures. Through these activities, the history of Sanuki Castle is being passed down to future generations.
The Significance of Visiting Sanuki Castle
Sanuki Castle is a rare example of a castle in Chiba Prefecture with stone walls, and its long history—over 400 years from the Muromachi period to the end of the Edo period—makes it a truly valuable site. Few places offer the opportunity to experience the grand sweep of Japanese history, from the fierce battles of the Sengoku period to the peaceful domain administration of the Edo period, all within a single castle site.
By combining a visit to the castle ruins with a stroll through the castle town, where buildings from the Edo period to the Showa era remain, you can experience history in a more nuanced way. Under the concept of “Edo – Showa – Towards a Future of Passing on Stories,” Sanuki Castle and its surrounding town offer a place to experience the continuity of history connecting the past, present, and future.
Inquiries
For detailed information about Sanuki Castle ruins and the castle town, as well as information on tours and events, please contact us below.
Futtsu City Construction and Economic Affairs Department, Commerce and Tourism Division
- Address: 2443 Shimo-Iino, Futtsu City, Chiba Prefecture
- Phone Number: 0439-80-1291 (Main)
- Official Website: Tourism Information Page on the Futtsu City Official Homepage
Checking the latest information before your visit will allow for a more fulfilling exploration of Sanuki Castle. Information on seasonal events and special openings is also available, so please feel free to inquire.
Summary
Sanuki Castle in Futtsu City, Chiba Prefecture, is a valuable castle ruin that has witnessed over 400 years of history, from the turbulent Sengoku period to the peaceful Edo period. It was a strategic point during the Sengoku period, repeatedly contested by the Mariya Takeda, Satomi, and Hojo clans, and during the Edo period, it served as the political center of the Sanuki Domain.
As the only castle in Chiba Prefecture with a stone wall turret base, and with well-preserved earthworks and dry moats, it is a castle ruin rich in points of interest. Furthermore, the castle town retains old buildings dating from the Edo period to the Showa era, and under the concept of “Edo to Showa to the Future: Passing on the Story,” efforts are being made to preserve the historical streetscape.
Access is excellent, and it can be easily visited using the Tateyama Expressway or the JR Uchibo Line. In addition to visiting the castle ruins, you can enjoy a fulfilling historical exploration of the Boso Peninsula by combining a stroll through the castle town and visiting surrounding tourist spots.
Sanuki Castle is perfect not only for history buffs but also as a holiday destination for families. Be sure to visit this historic castle ruin and castle town and experience the historical romance of Boso.
