Katsurayama Castle

Susono, Japan, Japan

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Katsurayama Castle (also written Kazurayama Castle) is a ruined Sengoku‑period mountain castle on the summit of Mount Atago in Susono, Shizuoka Prefecture, on the eastern ridge of Mount Ashitaka, about 270 meters above sea level.

It was originally the stronghold of the local Kazurayama clan, who held lands bordering three powerful families—Ieyasu’s rivals Imagawa, Takeda, and Hōjō—and so were forced to constantly balance alliances before finally siding openly with the Takeda in 1568. The Hōjō and Imagawa then took the castle temporarily, but the Takeda regained control and forced Kazurayama Ujimoto to adopt Takeda Shingen’s sixth son; when Ujimoto was later accused of treason in 1573, he was executed and the castle came fully under Takeda rule.

In March 1557, the famous Takeda general Baba Nobuharu had already led a 6,000‑man assault that destroyed the castle and killed its garrison, and after the Takeda clan collapsed in 1582 the site was abandoned and never rebuilt, leaving only earthworks and trenches as a local historic site. Visitors today reach the ruins by walking from Iwanami Station on the Gotenba Line (about 45 minutes) and then following a path through a cemetery beside a temple to climb the hill, where the site is accessible at any time and retains a quiet, undeveloped mountain setting.