What's new

Welcome to Japan Reference (JREF) - the community for all Things Japanese.

Join Today! It is fast, simple, and FREE!

Castle Iwadono Castle

This article is in the series Walking the Japanese Castles
Iwadono Castle (岩殿城 Iwadono-jō) is a hilltop castle located in Otsuki, Yamanashi Prefecture. Arriving at JR Otsuki Station, you will find a huge cliff towering on the northern side of the valley: over 150 metres in height, Iwadonoyama is a magnificent rock. Iwadono Castle was constructed on top of Mount Iwadono and was known as impregnable in the Sengoku Period.



In the ninth century, a Buddhist temple of the Tendai School, Entsu-ji (円通寺), was founded on the mountain. The temple complex, a famous place of practice in the 13th century, was known as Iwadono Gongen (岩殿権現). Later, the Oyamada clan made Iwadonoyama their base. Initially opposed to the Takeda, the Oyamada were subdued in 1509 and served the Takeda. Iwadono Castle was a strategically important fortress in the border regions of the Kai, Sagami and Musashi provinces. Gunnai District also linked the Kantō Plain to the Kōfu Basin.

After having been defeated by the forces of Oda Nobunaga and Tokugawa Ieyasu in the Battle of Tenmokuzan (天目山の戦い Tenmokuzan no Tatakai) in 1582, Takeda Katsuyori, the son of Takeda Shingen, burned down Shinpu Castle (in modern-day Nirasaki City, Yamanashi) and escaped to Iwadono Castle to seek shelter with Oyamada Nobushige (小山田信茂, 1545-1582), one of Shingen's Twenty-Four Generals. Nobushige, however, denied entry to Katsuyori and his entourage. Katsuyori, his wife, Hōjō Masako, and his son Nobukatsu all committed seppuku at Mount Tenmoku while the Takeda's last handful of followers fended off the enemy. The end of the Takeda clan had come. Nobushige was later executed by Nobunaga for his "un-samurai-like" comportment.


The northern and southern side of Mount Iwadono consists of precipitous cliffs. There are routes on the eastern and western side of the mountain, but, narrow and steep, they do not allow for the movement of larger troop contingents. Furthermore, Katsura River runs in a deep valley south of the castle and Kazuno River in the east. The mountaintop itself was relatively flat which is where the man and the second enclosure, as well as a riding ground, were established.


The map is based on the Digital Japan Portal Web Site powered by the Geospatial Information Authority of Japan, the location of the enclosures are based on my estimates.

Having spent the day in Kōfu, I arrived at JR Otsuki Station at 4 pm. Because there was no time, I hurried to the castle. Walking along the track, crossing the Katsura River, I reached the starting point of the Mount Iwadono path. If you arrive by car, there is a parking lot near the bridge.

① The starting point of the climb up Mount Iwadono.


② The information centre and museum at the base of the mountain. However, it had already closed at 4 pm. I had to push on to return before sunset.


The site of Agekido Gate. Close to the ridge, it was a strong and natural gate.


③ The largest open space on top of the ridge was very constricted but said to be used as a riding ground. While steep mountain fortresses offer ideal natural defence, they are very limited in terms of troops and material.



④ Finally, I arrived at the main enclosure. It had taken me a good hour from the station at a brisk pace. However, it was quite disappointing to see the radio installations after such a hard climb. Interestingly, Mount Iwadono has an altitude of 634 metres which is exactly the height of Tokyo Sky Tree (of course, their relative height is different).


This was a trench at the eastern side of the main enclosure, this narrow and slip slope was quite a challenge.


Below, the view from the observatory on the former riding grounds. When the Takeda sent their troops to Kantō, they would march through this valley.


Since I had started to walk the castles, my legs should have gained strength, but I suffered from terrible muscle aches after climbing Iwadono Castle.

Date of visit: 17 August 2013


  • Address: Nigiokamachi Iwadono, Otsuki-shi, Yamanashi
  • Transportation: a 20-minute walk from JR Chuo line Otsuki Station to the foot of the mountain
    3 kilometres from Chuo Expressway Otsuki Interchange via National Route 20
  • Other sights: Mt. Iwadono Guide Map (Otsuki City Website, in Japanese)


About author
Hiroto Uehara
Hiroto is an ordinary Japanese office worker, but his true mission is searching for castles on the weekend.


Very nice write-up! I have been cycling there a couple of times, usually starting at Otsuki Station, then taking R139 up to Matsuhime-toge. I guess we need to stop at Iwadono Castle next time. :)

Article information

Hiroto Uehara
Last update

More in Yamanashi

More from Hiroto Uehara

Share this article

Top Bottom