Tosadomari Castle, Naruto City, Tokushima Prefecture – The Complete Picture of a Pirate Castle that Flourished as a Base for the Awa Navy
What is Tosadomari Castle?
Tosadomari Castle is a hilltop castle from the Sengoku period located in Tosadomariura, Naruto-cho, Naruto City, Tokushima Prefecture. Built on the eastern part of Ogejima Island, this castle was an important base controlling a crucial point for maritime traffic at the entrance to the Kii Channel and the Seto Inland Sea. Currently protected as a Naruto City designated historical site, it is a valuable historical site that conveys the history of the Awa Navy.
The castle ruins are currently located within the grounds of Nankai Hospital, and public visits are restricted. However, its historical value is extremely high, and it is attracting attention from researchers as a typical example of a pirate castle from the Sengoku period.
History of Tosadomari Castle
Construction and the Rise of the Mori Clan
Tosadomari Castle was built during the Tenbun era (1532-1555). It is said that the castle’s origins lie in the fact that Morimotomura, son of Sada Kurobei, who migrated from Kuroda Village in Myoto District to Tosadomari in Itano District (present-day Naruto City), built a castle in this area.
Morimotomura, as the leader of the Awa naval force, controlled the sea area from the Kii Channel to the Seto Inland Sea. At that time, maritime traffic was extremely important for the transport of goods and military operations, and Tosadomari Castle functioned as a base for this. The Mori clan, as leaders of the naval force, played a crucial role in securing maritime interests in Awa Province.
The Invasion of Chosokabe Motochika and the Resistance of Tosadomari Castle
The most important event in the history of Tosadomari Castle was the invasion of Awa Province by Chosokabe Motochika in 1582. Chosokabe Motochika, a Sengoku period daimyo of Tosa Province, invaded Awa Province with the aim of unifying Shikoku. While many castles fell one after another, Tosadomari Castle is known as one of the few that continued to resist.
The Mori clan, leading the Awa naval force, fortified the castle’s defenses from the sea, making the most of its geographical advantages. Its location facing the Konaruto Strait was advantageous against attacks from the sea, and securing supply lines was also easy. This strategic location, combined with the Mori clan’s skillful defenses, allowed Tosadomari Castle to withstand the fierce attacks of the Chosokabe army.
Service to Hachisuka Iemasa and Relocation to Tsubakidomari
In 1585, during Toyotomi Hideyoshi’s conquest of Shikoku, Chosokabe Motochika surrendered, and Hachisuka Iemasa became the new lord of Awa Province. The Mori clan flexibly adapted to this political change and chose to serve the new lord, Hachisuka Iemasa.
In 1586 (Tensho 14), the Mori clan moved their residence from Tosadomari Castle to Tsubakidomari. This relocation is believed to have been based on Hachisuka Iemasa’s domain management policies, and the Mori clan continued to maintain their position as leaders of the Awa naval force while fulfilling their role under the new system.
Tosadomari Castle was later abandoned, but its history as a thriving base for the Awa naval force is still recounted today as an important cultural heritage of the region.
Structure and Characteristics of Tosadomari Castle
Characteristics as a Pirate Castle
Tosadomari Castle is a naval base castle also known as a “pirate castle.” Built on a hill overlooking the Konaruto Strait in the eastern part of Ogejima Island, it possessed ideal locational conditions for monitoring and controlling maritime traffic.
The castle’s structure took the form of a flatland castle, with the main enclosure located on a low-lying hill slightly inland from the coastline. This provided a defensive system that ensured visibility from the sea while also being able to withstand attacks from land.
Layout and Remains
The layout of Tosadomari Castle is presumed to have been a multi-enclosure structure with multiple enclosures arranged around a central enclosure. While detailed investigation is difficult due to the current site being occupied by Nankai Hospital, the remaining topography allows for inferences about the castle’s structure at the time.
The south side of the castle faced Okazaki Beach, a convenient location for supplying goods from the sea and for ships to enter and leave the port. Furthermore, its strategic position allowed for monitoring ships passing through the Konaruto Strait, controlling a key point in maritime traffic.
It is believed that defensive structures such as earthworks and moats were also constructed, giving the castle a complex structure combining the functions of a pirate castle and a land fortress.
Place Name and Historical Background of Tosadomari
Origin of “Tosadomari”
The place name “Tosadomari” has an interesting history. The “Tosa Diary,” written by the Heian period nobleman Ki no Tsurayuki upon his return to Kyoto from Tosa Province (present-day Kochi Prefecture), records his stay in this region. The most widely accepted theory is that the name “Tosadomari” (Tosa Port) originated from the fact that ships sailing from Tosa to Kyoto would wait here for favorable winds and tides. It was recognized as a vital point for maritime traffic from ancient times, and it is clear that it functioned as a port where ships anchored.
This historical background is deeply related to why the Mori clan established a naval base here during the Sengoku period (Warring States period). The geographical condition of being a key point for maritime traffic since ancient times was a major factor in its selection as the location for the construction of Tosadomari Castle.
Geographical Importance of Ogejima Island
Ogejima Island, where Tosadomari is located, is situated northeast of Naruto City and separated from the Shikoku mainland by the Konaruto Strait. The island contains five settlements: Fukuike, Oge, Kuroyama, Otani, and Tosadomari, collectively known as Tosadomariura, Naruto Town.
Located at a crucial point on the maritime trade route connecting the Kii Channel and the Seto Inland Sea, Ogejima Island played a vital role in monitoring and controlling maritime traffic from ancient times through the Sengoku period and into the Edo period. Tosadomari Castle was a fortress that made the most of this geographical advantage.
The Awa Navy and the Mori Clan
The Role of the Awa Navy
The Awa Navy was a naval organization that protected maritime interests and controlled maritime traffic in Awa Province during the Sengoku period. Centered around the Mori clan, the Awa Navy operated in a vast sea area stretching from the Kii Channel to the eastern Seto Inland Sea.
The navy’s main duties included guarding maritime trade routes, suppressing piracy, escorting supply transports, and conducting maritime operations during wartime. They also gained economic benefits, particularly by controlling the distribution of marine products such as salt and fish.
Morimotomura and Morimura Haru
Morimotomura, who built Tosadomari Castle, was renowned as the leader of the Awa naval force. He was not merely a military commander, but also a maritime lord well-versed in the practicalities of maritime traffic. The Mori clan, for generations, continued to protect the maritime interests of Awa Province as leaders of the navy.
Morimura Haru, who succeeded Morimotomura, also played an active role in leading the Awa naval force, just like his father. He is known for playing a crucial role in the defense of Tosadomari Castle during the invasion of Chosokabe Motochika, and for successfully defending the castle.
Even after serving Hachisuka Iemasa, the Mori clan was highly valued as naval experts and continued to play a central role in the maritime defense of the Awa Domain.
Current Status of Tosadomari Castle Site
Protection and Current Status as a Historic Site
The Tosadomari Castle site is protected as a historical site designated by Naruto City. However, it is currently located within the grounds of Nankai Hospital, and access is restricted to authorized personnel only. Therefore, it is difficult for general castle enthusiasts and history buffs to freely visit the site.
While the city of Naruto is considering the maintenance and public access to the castle ruins as a future issue, its nature as a medical facility makes immediate public access difficult. However, its value as a historical site is recognized, and the formulation of a future preservation and utilization plan is expected.
Nearby Historical Spots
When visiting the Tosadomari Castle ruins, we recommend also visiting the surrounding historical spots. Many other castle ruins and historical sites are scattered throughout Naruto City, allowing you to experience the Sengoku period history of Awa Province.
Tsubakidomari, where the Mori clan relocated, is also located on Ogejima Island and is an important place for understanding its connection to Tosadomari Castle. Furthermore, a beautiful coastline stretches along the Konaruto Strait, offering views of the sea area where the Awa naval forces once operated.
Okazaki Beach is located south of Tosadomari Castle, allowing you to imagine the view of the sea from the castle. It’s an ideal spot for a historical walk, allowing you to experience how the naval forces monitored the sea at that time.
Access and Visiting Information
Access to Tosadomari Castle Ruins
Location: Tosadomariura, Naruto-cho, Naruto City, Tokushima Prefecture
Access by Car:
- Approximately 15 minutes from the Naruto Kita Interchange on the Kobe-Awaji-Naruto Expressway
- Approximately 20 minutes from Naruto city center via prefectural roads
- Parking: There is a parking lot at Nankai Hospital, but its use for castle ruins visits is restricted.
Public Transportation:
- Approximately 25 minutes by Naruto City Bus or taxi from JR Naruto Station
- Take a bus bound for Ogejima and get off at the Tosadomari bus stop.
Notes for Visitors
As mentioned above, Tosadomari Castle Ruins are currently located within the grounds of Nankai Hospital, and general access is restricted. Please avoid entering the grounds without permission and limit your visit to viewing from the outside.
From the roads and public areas surrounding the castle ruins, you can observe the topography of the hill where the castle once stood. Furthermore, strolling along the Naruto Strait allows you to experience the atmosphere of the sea area where the Awa naval forces were active.
You can obtain materials and information about Tosadomari Castle from the Naruto City Board of Education and the Naruto City Library, so it is recommended to inquire before your visit.
Contact Information:
- Naruto City Hall, Cultural Properties Division
- Address: 170 Higashihama, Minamihama, Muya-cho, Naruto City, Tokushima Prefecture 772-8501
- Phone: 088-684-1111 (Main)
Cultural Value of Tosadomari Castle
Importance in Pirate Castle Research
Tosadomari Castle is an important example in the study of the unique type of castle known as a “pirate castle” in the history of Japanese castles. While many naval bases existed along the Seto Inland Sea coast, Tosadomari Castle holds unique value as a castle that controlled the Kii Channel, a special sea area.
With its strategic location controlling a key point in maritime traffic, a layout designed for naval operations, and defensive capabilities that withstood the invasion of Chosokabe Motochika, this castle retains many characteristics of a pirate castle and is attracting attention from castle researchers.
Significance in Local History
Tosadomari Castle holds an important position in the local history of Naruto City and Tokushima Prefecture. As a base of operations for the Awa naval force, it provides concrete evidence that this region was a key point for maritime traffic from ancient times.
As a historical site that tells of the achievements of the Mori clan, a powerful local warlord, it is also an important teaching material in local history education. Furthermore, it is an interesting place from a literary history perspective, such as its connection to the Tosa Diary.
Recommended Route for Visiting Tosadomari Castle
Ogejima Historical Walking Course
This route focuses on the Tosadomari Castle ruins and explores historical spots on Ogejima Island.
- Observation Spot for the Konaruto Strait: First, enjoy the view of the Konaruto Strait and identify the area where the Awa naval forces were active.
- Around the Tosadomari Castle Ruins: Observe the topography of the castle ruins from the outside and confirm their relationship to the sea.
- Okazaki Coast: Imagine the ships coming and going at the coast located south of the castle.
- Towards Tsubakidomari: Move to the Tsubakidomari area, where the Mori clan relocated, and understand the relationship between the two locations.
- Exploring the Villages on Oge Island: Visit historical villages such as Fukuike, Oge, and Kuroyama.
Related Historical Sites in Naruto City
Besides Tosadomari Castle, there are many other historical sites in Naruto City.
- Muyō Castle Ruins: Castle ruins located in the city of Naruto, an important base for the Hachisuka clan.
- Naruto City Library: Has a rich collection of local historical materials, including documents on Tosadomari Castle.
- Ōasahiko Shrine: A shrine that has long been revered as the Ichinomiya (first-ranked shrine) of Awa Province.
By combining these spots, you can gain a deeper understanding of the Sengoku period history of Awa Province.
Reference Materials Regarding Tosadomari Castle
Major Literature and Materials
For those who want to learn more about Tosadomari Castle, here are some major reference materials:
- “Naruto City History”: The official city history of Naruto City, containing a detailed description of Tosadomari Castle.
- “Castles of Tokushima Prefecture”: A book comprehensively introducing castles in Tokushima Prefecture.
- “Research on the Awa Naval Force”: An academic book specializing in the activities of the Awa Naval Force.
- Cultural Property Survey Report published by the Naruto City Board of Education
These materials can be viewed at the Naruto City Library and the Tokushima Prefectural Library.
Online Information Sources
- Naruto City Official Website: Basic information on Tosadomari Castle Ruins, designated as a city cultural property, is posted.
- Castle Information Websites such as Kojodan and Nippon Joryu: Visit records and photos are shared.
- Tokushima Prefectural Board of Education Cultural Property Database: Historical site information within the prefecture can be searched.
Summary: Historical Significance of Tosadomari Castle
Tosadomari Castle, built on Ogejima Island in Naruto City, Tokushima Prefecture, is a historical site of unique value in the history of Japanese castles, as a pirate castle from the Sengoku period. As the residence of the Mori clan, who led the Awa naval force, it controlled a key point for maritime traffic connecting the Kii Channel and the Seto Inland Sea, and was a strong castle that withstood the invasion of Chosokabe Motochika.
Although it is currently located on the grounds of Nankai Hospital and not open to the public, it is protected as a Naruto City designated historical site, and its historical value is widely recognized. Given its connection to the Tosa Diary, its role as a base for the Awa naval force, and its value as a historical site that tells the story of maritime traffic during the Sengoku period, further research, preservation, and utilization are expected in the future.
When visiting Naruto City, we hope you will reflect on the history of Tosadomari Castle while enjoying the beautiful coastline of Ogejima Island and the scenery of the Konaruto Strait, allowing you to feel the atmosphere of the era when the Awa naval force was active. Tosadomari Castle is an indispensable and important historical site for understanding the history and culture of the region.
