Okō Castle

Architecture, patrimoine et histoire · Préfecture de Kōchi

Okō Castle stands on the summit of Mount Okō, a 97-metre hill overlooking the Kokubu River at the north-western edge of the Kōchi plain, in what is now Nankoku. It was here that the Chōsokabe clan, settled in Tosa Province since the Kamakura period, kept its seat for several generations. Lost in 1508 to a coalition of neighbouring lords, the stronghold was recovered by Chōsokabe Kunichika around 1518 with the backing of the Ichijō. His son Motochika made it the starting point of a meteoric rise: master of the Kōchi plain around 1570 and of all Tosa in 1575, he extended his power over the whole of Shikoku in 1585 before submitting to Toyotomi Hideyoshi that same year. The clan seat moved to Ōtakasaka in 1588, then to Urado in 1591, and Okō was abandoned. No buildings survive, but the terrain preserves the layout of a medieval mountain castle: a summit platform, stepped terraces, earthen ramparts, dry moats, a well and low stone walls uncovered during excavations from 1985 to 1990. A National Historic Site since 2008 and listed among the Continued 100 Fine Castles of Japan, it hosts the Kōchi Prefectural Museum of History on one of its terraces.