Complete Guide to the History and Highlights of Iinoya Castle | A Thorough Explanation of the Mountain Castle Associated with Ii Naotora
What is Iinoya Castle?
Iinoya Castle is a medieval mountain castle located in Iinoya, Inasa-cho, Hamana-ku, Hamamatsu City, Shizuoka Prefecture. Known as the birthplace of the Ii clan, a prominent family in Totomi Province, it is a historical castle that gained nationwide attention, particularly through the NHK Taiga drama “Onna Jōshu Naotora” (The Lady Warlord Naotora).
Built on the summit of a small mountain 115 meters above sea level, the castle occupies a strategically important location north of the confluence of the Iinoya River and the Jingūji River. Currently, it is protected as a Hamamatsu City designated historical site and is open to the public as Iinoya Castle Ruins Shiroyama Park.
From the castle ruins, you can enjoy a panoramic view of the town of Iinoya, and on clear days, you can even see as far as Lake Hamana. This excellent view speaks to the military surveillance function the castle once possessed.
History of Iinoya Castle
Origins of the Ii Clan and the Place Name of Iinoya
The history of Iinoya is ancient, dating back to the Nara period. In 713 (Wado 6), this area was renamed from “Igo” to “Iigo,” which became the origin of the current place name “Iinoya.”
In 733 (Tenpyo 5), it is said that the high priest Gyoki founded Jizo-ji Temple (later Ryotan-ji Temple) in this area. This temple later became the family temple of successive generations of the Ii clan and played an important role as the spiritual pillar of the Ii family.
There are various theories about the founder of the Ii clan, but it is believed that they established their residence in this area around the Kanko era (1004-1012) in the mid-Heian period. The Ii clan developed as local lords of Totomi Province, expanding their power centered around Iinoya.
Iinoya Castle in the Sengoku Period
During the Sengoku period, the Ii clan served under the Imagawa clan. Iinoya Castle is believed to have functioned as a peacetime residence for the Ii clan, a so-called “hilltop castle,” with Mitake Castle, a more formidable mountain castle, as their main base.
The most dramatic turning point in the history of the Ii clan occurred in 1562 (Eiroku 5). The then-head of the clan, Ii Naotora, was tragically murdered by Imagawa Ujizane. Naotora was also the father of Ii Naomasa, who later became famous as one of the Four Heavenly Kings of Tokugawa.
After Naotora’s death, the Ii clan faced a crisis of survival. Naotora’s eldest son, Toramatsu (later Ii Naomasa), was still a child and unable to inherit the family headship. In this critical situation, Ii Naotora (Jirohōshi), Naotora’s fiancée, became the head of the Ii clan and supported the family.
The Era of Ii Naotora, the Female Castle Lord
Ii Naotora became the lord of Iinoya Castle, an extremely rare female castle lord during the Sengoku period. Although she had been a nun, she is said to have returned to secular life to protect the Ii family name and wielded the leadership of the family.
Naotora’s time as castle lord was fraught with difficulties. Facing numerous challenges, including pressure from the Imagawa clan, relations with the Tokugawa clan, and controlling her retainers, she protected the Ii family until her young son, Toramatsu, came of age.
In 1568 (Eiroku 11), when Tokugawa Ieyasu began his invasion of Tōtōmi Province, the situation in Iinoya changed dramatically. Naotora displayed skillful diplomacy, guiding the Ii clan towards the Tokugawa side. This decision would lead to the later prosperity of the Ii family.
Ii Naomasa and the Tokugawa Era
Raised under the protection of Ii Naotora, Toramatsu came of age, took the name Ii Naomasa, and served Tokugawa Ieyasu. Naomasa achieved military success and rose to become one of the Four Heavenly Kings of the Tokugawa.
After the Battle of Sekigahara, Naomasa was transferred to Sawayama in Omi Province (later Hikone), and the Ii clan prospered throughout the Edo period as a hereditary daimyo. The Ii family of Hikone Domain produced Ii Naosuke, a powerful figure in the late Edo period, and became a family that played a central role in the Tokugawa shogunate.
Iinoya Castle was abandoned after the Ii clan’s transfer, but it has been carefully preserved to this day as the birthplace of the Ii clan.
Structure and Layout of Iinoya Castle
Basic Structure of the Castle
Iinoya Castle has the structure of a typical medieval mountain castle. This castle features a relatively simple layout, with the main enclosure (honmaru) located on the mountaintop and surrounded by earthen ramparts.
While the castle mountain’s elevation is 115 meters, relatively low for a mountain castle, the elevation difference from the surrounding plains is approximately 60 meters, providing sufficient height for defensive purposes.
The main enclosure is roughly circular in shape and leveled, with an estimated area of about 500 square meters. This size suggests it possessed the minimum necessary functions for a residence during peacetime.
Earthen and Stone Walls
Traces of earthen ramparts remain around the main enclosure on the mountaintop. Even today, earthen mounds about 1 meter high can be seen, offering a glimpse into the defensive structures of the time.
Traces of stone walls are also found in some areas, indicating that it was not simply an earthen castle, but that some stone was used. However, it is believed to have been a simpler, rough-hewn structure rather than a full-fledged stone wall like those found in early modern castles.
Remains of the Residence at the Foot of the Mountain
It is believed that there were sections called Honmaru and Nijomaru at the southern foot of the castle mountain. These are thought to have functioned as living spaces and administrative offices during peacetime, in contrast to the military facilities at the mountaintop.
The entire foot of the mountain constituted the castle grounds, and it is thought that it was used in a typical manner for medieval mountain castles: the mountaintop was used for siege during times of conflict, while the foot of the mountain was used for daily life during peacetime.
Relationship with Mitake Castle
Approximately 2 kilometers northeast of Iinoya Castle lies Mitake Castle, at an elevation of 466 meters. Mitake Castle was the main castle of the Ii clan, and was a fortified stronghold equipped with more robust defensive facilities.
It is thought that Iinoya Castle and Mitake Castle formed a “Negoya-style mountain castle” system, which could be used interchangeably in peacetime and wartime. Mitake Castle could be seen from Iinoya Castle, allowing for visual coordination between the two castles.
Highlights of Iinoya Castle
Development as a Castle Mountain Park
The current Iinoya Castle ruins have been developed as “Iinoya Castle Ruins Castle Mountain Park,” and are freely accessible to everyone. The path leading up to the castle has been developed into a walking trail, and it takes about 10-15 minutes to reach the summit on foot.
However, the path is quite steep, so we recommend wearing comfortable shoes. Particular caution is needed when descending.
View from the Summit
The greatest highlight of Iinoya Castle is the magnificent view from the summit. Standing on the site of the main enclosure, you can see the townscape of Iinoya below, experiencing the view that the former lords of the castle once saw.
On clear days, you can see Lake Hamana to the south. Also, to the northeast, you can see the mountain range where Mitake Castle is located, giving you a real sense of the Ii clan’s castle network.
One of its charms is the beautiful scenery you can enjoy throughout the seasons: cherry blossoms in spring, lush green mountains in the season of fresh greenery, and autumn leaves in the fall.
Earthworks and Leveled Areas
At the main enclosure on the mountaintop, you can observe the faint traces of earthworks. The earthworks surrounding the nearly circular leveled area are valuable remains that demonstrate the castle construction technology of the time.
The leveled area itself clearly shows traces of being artificially flattened, demonstrating the high level of civil engineering technology of the medieval period.
Observation Deck
An observation deck is installed at the mountaintop, offering panoramic views of the surrounding area from a higher vantage point. The view from this observation deck is exceptional and is a popular spot for commemorative photos of visitors to Iinoya Castle.
Information Boards and Explanation Panels
Information boards explaining the history and structure of Iinoya Castle are installed within the castle ruins. They provide detailed explanations of the history of Ii Naotora and the Ii clan, and reading them before visiting the castle ruins will provide a deeper understanding.
Nearby Attractions and Tourist Spots
Ryōtanji Temple
Located about a 10-minute walk from Iinoya Castle, Ryōtanji Temple is a must-see spot as the family temple of successive generations of the Ii clan. This ancient temple is said to have been founded in 733 (Tenpyō 5) by Gyōki and is also known as the temple where Ii Naotora became a nun.
The temple grounds contain the tombs of successive heads of the Ii family, including the graves of Ii Naomasa and Ii Naotora. Furthermore, the garden, a nationally designated scenic spot, is a beautiful pond garden said to have been designed by Kobori Enshū, offering beautiful scenery throughout the seasons.
The main hall displays valuable documents and treasures related to the Ii family, allowing visitors to learn deeply about the history of the Ii clan.
Iinoya Shrine
This shrine, dedicated to Prince Munenaga, a member of the imperial family during the Nanboku-chō period, was founded during the Meiji era. Prince Munenaga was a son of Emperor Go-Daigo and was active in Tōtōmi Province as a supporter of the Southern Court, with the Ii clan also providing support.
The temple grounds are enveloped in a tranquil atmosphere, a place where you can feel the history of Iinoya.
Iinoya Castle Ruins Regional Heritage Center
Located at the foot of Iinoya Castle, this facility features exhibits on the Ii clan and Iinoya Castle. Admission is free, and visiting before visiting Iinoya Castle will deepen your understanding.
A parking lot is also available, making it a convenient base for those arriving by car. The path to Iinoya Castle begins behind the center.
Mitake Castle Ruins
If you have the time and energy, we recommend visiting Mitake Castle, the main castle of the Ii clan. It is a more substantial mountain castle than Iinoya Castle, with well-preserved remains such as moats and baileys.
However, you will need to climb to the summit at an altitude of 466 meters, so mountain climbing equipment and preparation are necessary.
Exploring the Streets of Iinoya
The village of Iinoya retains its historic streetscape, evoking a sense of history. You can enjoy a leisurely stroll, especially around Ryōtanji Temple.
There are shops selling local specialties and souvenir shops selling goods related to Ii Naotora, making it perfect for creating lasting memories of your trip.
Access Information
Access by Public Transportation
By Train and Bus
- Take the Enshu Railway bus bound for Okuyama or Kiga from Hamamatsu Station on the JR Tokaido Main Line.
- Get off at the Jinguji bus stop and walk for approximately 15 minutes to reach the Iinoya Castle Ruins Regional Heritage Center.
- Since the number of buses is limited, we recommend checking the timetable in advance.
By Tenryu Hamanako Railway
- Get off at Kanazashi Station on the Tenryu Hamanako Railway and walk for approximately 30 minutes.
- Or get off at Kiga Station and take a taxi for approximately 10 minutes.
Access by Car
By Tomei Expressway
- Approximately 20 minutes from Hamamatsu-Nishi IC.
- Take National Route 257 towards Iinoya.
By Shin-Tomei Expressway
- Approximately 15 minutes from Hamamatsu-Inasa IC.
- Convenient access from the nearest interchange.
Parking
- Iinoya Castle Ruins Regional Heritage Center Parking Lot (Free)
- Ryōtanji Temple Parking Lot (For visitors, Free)
- Due to limited parking spaces, early arrival is recommended on weekends.
Estimated Time Required
- From parking lot to summit: 10-15 minutes on foot
- Sightseeing time at the summit: 20-30 minutes
- Visiting Ryōtanji Temple: 30-60 minutes
- Total time including exploring the surrounding area: 2-3 hours
Notes and Recommended Attire for Visitors
Clothing and Items to Bring
Since climbing to Iinoya Castle involves walking along mountain paths, the following preparations are recommended.
- Footwear: Comfortable sneakers or trekking shoes (heels and sandals are unsuitable)
- Clothing: Comfortable clothing, a jacket appropriate for the season
- Items to bring: Drinking water, towel, insect repellent (summer)
- Rain gear: Umbrella or rainwear during periods of unpredictable weather
Seasonal Highlights and Precautions
Spring (March-May)
- Particularly beautiful during cherry blossom season
- Mild weather, ideal for visiting
- May be crowded during Golden Week
Summer (June-August)
- Lush greenery and beautiful views
- Essential for staying hydrated and taking precautions against the heat
- Don’t forget insect repellent
Autumn (September-November)
- Beautiful autumn foliage and pleasant weather
- Most recommended season for visiting
- Bring a jacket as it gets chilly in the mornings and evenings
Winter (December-February)
- Clear air and best views
- Cold weather precautions are necessary
- Be careful as the road surface may freeze.
Safety Precautions
- The path to the castle is steep, so pay particular attention to your footing, especially on the descent.
- Be careful as the path can be slippery during or after rain.
- Avoid visiting alone; if possible, go with others.
- Do not push yourself if you are not feeling well.
- Plan to complete your descent before sunset.
Model Course for Enjoying Iinoya Castle
Half-Day Course (Approx. 3 Hours)
- Iinoya Castle Ruins Regional Heritage Center (30 minutes)
- View the exhibits and acquire background knowledge
- Restroom break
- Climbing Iinoya Castle Ruins (1 hour)
- Climbing the path to the castle (15 minutes)
- Enjoying the view from the summit (30 minutes)
- Descending (15 minutes)
- Visiting Ryotanji Temple (1 hour)
- Visiting the main hall and garden
- Visiting the Ii family cemetery
- Sightseeing in the Surrounding Area (30 minutes)
- Stroll through the streets of Iinoya
- Purchase souvenirs
One-Day Course (approx. 6 hours)
Morning:
- Visit Ryōtanji Temple (1 hour)
- Climb to Iinoya Castle Ruins (1.5 hours)
- Lunch (1 hour)
- Enjoy local cuisine at a local restaurant
Afternoon:
- Visit Iinoya Shrine (30 minutes)
- Iinoya Castle Ruins Regional Heritage Center (30 minutes)
- Climb to Mitake Castle Ruins (2 hours) *For those confident in their physical fitness*
- Or tour of surrounding historical sites
Comprehensive Course for History Fans (1 night, 2 days)
Day 1:
- Morning: Visit Hamamatsu Castle
- Afternoon: Move to the Iinoya area, visit Ryōtanji Temple and Iinoya Castle Ruins
- Evening: Overnight stay at Kanzanji Onsen
Day 2:
- Morning: Visit to Mitake Castle Ruins
- Afternoon: Sightseeing around Kiga Checkpoint and Lake Hamana
Cultural Value and Preservation Activities of Iinoya Castle
Value as a Historic Site
Iinoya Castle is a valuable historical site for understanding the castles of local lords during the transitional period from the medieval to the early modern period. Its preservation of the medieval mountain castle form without being remodeled into a large-scale early modern castle is considered academically significant.
It is protected as a Hamamatsu City designated historical site, and appropriate preservation and utilization are expected in the future.
Ii Naotora and Regional Development
The 2017 NHK Taiga drama “Onna Jōshu Naotora” (Female Castle Lord Naotora) brought Iinoya Castle nationwide attention. Taking this as an opportunity, the region is actively promoting tourism centered around Ii Naotora.
The establishment of a regional heritage center, the improvement of information boards, and the implementation of guided tours have significantly enhanced visitor facilities.
Future Prospects
Further research and investigation of the Iinoya Castle ruins are underway, and new discoveries are expected. Furthermore, the use of VR technology to recreate the castle as it once was is being considered, creating a space where more people can experience history.
Summary
Iinoya Castle is a mountain castle in Hamamatsu City, Shizuoka Prefecture, and the birthplace of the Ii clan. Built on a 115-meter-high mountain, it holds historical significance as a place associated with the female lord Ii Naotora and Ii Naomasa, one of the Four Heavenly Kings of Tokugawa.
Currently, it is maintained as Shiroyama Park, where visitors can enjoy magnificent views from the mountaintop. The surrounding area is dotted with historical sites, including Ryōtanji Temple, the Ii clan’s family temple, making it a valuable area to experience the history of the Ii clan.
The ruins of Iinoya Castle, which retain the atmosphere of a medieval mountain castle, are a recommended spot not only for history buffs but also for those who want to enjoy nature and scenery. When sightseeing in Hamamatsu, be sure to visit Iinoya Castle and feel the spirit of the Sengoku period.
The story of the Ii clan, which began as a small mountain castle in Totomi Province, eventually developed into a large domain that supported the Tokugawa shogunate. Enjoy a journey to experience the romance of history at Iinoya Castle, the origin of this clan.
