Koumyo Castle

Kōmyōjō is a yamajiro (mountaintop castle) ruin on the border of the townships of Saku and Yokokawa in the Tenryū Ward of Hamamatsu Municipality. Ruins remain in the form of earthworks such as baileys and trenches. There is a horikiri (trench) behind a series of terraced baileys which is the most di

History

Kōmyōjō was built circa 1530 by Asahina Tokishige, a vassal of Imagawa Ujiteru. The succeeding lord was Asahina Yasukata. Around 1570, the castle fell into the hands of Takeda Shingen, with Asahina Matatarō as castellan. In 1575, Tokugawa Ieyasu ordered Honda Tadakatsu and Sakakibara Yasumasa to capture Kōmyōjō. They did so, and Ôkubo Tadayo, lord of Futamatajō, took ownership of the fort following the battle of Nagashino. Kōmyōjō is believed to have been abandoned in 1582 following the demise of Takeda Katsuyori.

Field Notes

Kōmyōjō is a yamajiro (mountaintop castle) ruin on the border of the townships of Saku and Yokokawa in the Tenryū Ward of Hamamatsu Municipality. Ruins remain in the form of earthworks such as baileys and trenches. There is a horikiri (trench) behind a series of terraced baileys which is the most distinctive medieval fortification feature (exploring here I briefly saw a serow).

The beautiful stone-piled walls seen on-site today, known as the 'ruins of Mount Kōmyō', were built for a temple in the Edo period, Kōmyōji, which burnt down in 1931. These walls were built after the fort's time, and likely much of the medieval fort's structure was lost to the temple's construction. However, curiously, the layout of the temple does appear fort-like in places, particularly the steep terraces, and the main enclosure even has an elevated mound to the rear with a platform flanking the entrance. This strikes the castle-enthusiast as turret-like, and it's easy to imagine that the temple followed the fort's existing structure here. As to what purpose this platform served the temple, perhaps a belfry was erected atop there.

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Gallery

"Main Bailey" from below, and temple ishigaki
Stone-lined ramp structure
Yaguradai-like structure
Temple depiction
Temple depiction
Temple depiction
Dorui-like structure in lower bailey
Lower "bailey" with dorui-like structure surrounding
Dorui
Forest map
Rampart-like structure
Site entrance
Stone-lined ramp structure
Ishigaki
Bailey space in medieval area
Well in medieval castle ruin
Horikiri (trench)
Earthworks
Dorui
Bailey space in medieval area
Dorui

Castle Profile
English Name	Koumyo Castle
Japanese Name	光明城
Founder	Asahina Tokishige
Year Founded	c.1530
Castle Type	Mountaintop
Castle Condition	Ruins only
Historical Period	Pre Edo Period
Artifacts	Horikiri
Features	trenches, stone walls
Visitor Information
Access	Ippukudokoro-Yokokawa Roadside Station on Route 362; 10 min walk to trailhead; 100 min hike.
Hours	24/7 free; mountain
Time Required	60 mins
Location	Hamamatsu, Shizuoka Prefecture
Coordinates	34.91782, 137.85951
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Admin
Added to Jcastle	2025
Contributor	ART
Admin Year Visited	Viewer Contributed
Friends of JCastle
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Shiseki no Yawa
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