Remains of Washi Castle

Oyama, Japan, Japan

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The Remains of Washi Castle are the ruins of an early medieval flatland castle in Oyama City, Tochigi Prefecture, Japan, which served as the original seat of the Oyama clan from the Kamakura period and became one of the clan’s five key strongholds during the Muromachi period.

Built on a river terrace along the Omoigawa River, the castle was likely constructed in the 14th century, possibly by Oyama Masamitsu or Oyama Yoshimasa, and functioned as the main base of the Oyama forces during the 1380–1383 rebellion against the Kamakura Kubo; when that conflict intensified, the clan eventually withdrew from Washi Castle to Gion Castle, and the site was abandoned around 1601 when the Oyama clan was transferred to Echizen Province by the Tokugawa shogunate.

Today, the remains are designated as part of the “Oyama Clan Castle Ruins” (together with Oyama Castle and Nakakuki Castle) and form a National Historic Site since 1991, with the inner enclosure largely occupied by Washi Shrine (Washijinja) and the outer areas lost to modern residential development, while visible traces include turret bases (yagura‑dai), earthen ramparts, and dry moats that outline the former main, middle, and outer baileys.

The site is accessible on a roughly 30‑minute walk from Oyama Station on the JR Tōhoku Main Line, Mito Line, or Ryōmō Line, and is maintained as part of Oyama Comprehensive Park, offering a quiet, historically rich spot where visitors can walk among moat remnants and shrine grounds and sense the layout of a medieval Kanto‑region stronghold.