Kōkokuji Castle

Kōkokuji Castle is a mountain fortress in Numazu, Japan, built on the southern slopes of Mount Ashitaka with four main enclosures arranged in a straight line from north to south. The site follows the natural topography and relies on steep earthen ramparts and a deep dry moat for defense.

Ise Shinkuro Moritoki, who later adopted the name Hojo Soun, took control of the fortress in 1487 after supporting the Imagawa clan in a succession dispute. His descendants transformed the region into a base for their further expansion into eastern Japan.

The name reflects Buddhist traditions that were part of the regional identity during the feudal era. Local interpretations of military architecture remain visible in the layout of defensive earthworks that once protected the enclosures.

Travelers reach the ruins by taking the Fujikyu City Bus from JR Numazu Station South Exit to the Higashi-Negoya stop. The walk to the main enclosure follows wooded slopes and requires sturdy footwear due to uneven ground.

Excavations at the main bailey uncovered foundations of two buildings without roof tiles, suggesting an unusual construction method for Japanese fortifications of that period. This detail leads researchers to believe the structures were erected quickly and provisionally.