Ioto Castle


Iotojou (1).JPG


Iotojō was built as a fortified signal tower by Inukai Hanzaemon, a vassal of the Ogasawara Clan, who were hegemonic in Shinano at that time (early 16th century). The fort is mentioned as having played a role in the battle of Shiojiri Pass, which is located to the south, in 1548. The Shiojiri Pass is a strategic area at the site of a bottle neck between the counties of Suwa and Ina. Ogasawara forces were defeated at the pass by Takeda Shingen, and the battle there is said to have demonstrated the superlative cavalry tactics of Takeda forces. There is some indication that Iotojō was intended to be expanded but construction was halted, perhaps because of the Ogasawara defeat at the pass, or because the fort was located too far from the pass to effectively control it.

Visit Notes

Iotojō is a wild yamajiro (mountaintop castle) in a relatively remote corner of Shiojiri Municipality. The road to the castle is very steep, and the trail starts next to a bridge where the road is closed. It’s quite a challenge to climb to this fort ruin. It is steep and there are rope sections (one of which I repaired; I’m no boy scout but I know I did a good job with the knot because it didn’t give when I later used it to descend!).

The fort is a single bailey complex fort with terracing to the front and rear (a single lip to the immediate rear). The main bailey is partially divided by terracing, leaving an uneven terrain. There is a hokora (mini-shrine) in the main bailey now. The sides of the bailey are very steep. To the rear is a ridge which has been collapsed by landslides so that now it is more like a climbing frame of tree roots than it is solid ground. If one goes over this ridge, on which the soil is so loose it sinks beneath one’s feet, one will come to a gnarly rockface with an ancient rope going up it. Climbing this uninviting path, trusting in a dubious rope, is no mean feat, but on the more intact portion of the ridge above is a series of terraced baileys ending in a horikiri (trench). This site is fairly dangerous to master.

  • Main bailey

Castle Profile
English Name Ioto Castle
Japanese Name 五百渡城
Alternate Names 五百渡砦
Founder Inukai Hanzaemon
Year Founded Early 16th Century
Castle Type Mountaintop
Castle Condition Ruins only
Historical Period Pre Edo Period
Artifacts Kuruwa, Horikiri
Features trenches
Visitor Information
Access Nearest Station is Midoriko on the Chūō Line
Visitor Information 24/7 free; mountain
Time Required 60 minutes
Website 22.html
Location Shiojiri, Nagano Prefecture
Coordinates 36° 6' 42.41" N, 138° 1' 13.44" E
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Added to Jcastle 2022
Contributor ART
Admin Year Visited Viewer Contributed
Friends of JCastle

(one vote)
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10 months ago
Score 0++
Gets a 3 for the thrill factor.