Oka Castle is located on the top of Tenjinyama, a long hill to the east of the urban center of Taketa, which is situated in a small basin in the southwestern part of
Bungo Province. It is at a crossroads of various roads crisscrossing the island of
Kyushu and because of its geographical position, occupies an important strategic point controlling western Bungo Province. The site is flanked by two rivers, the Inaba River and the Tamaki River, tributaries of the
Ōno River, which merge just to the east of the castle. The fortifications spread at the narrow east part of the hill, which has an elevation of 325 meters above sea level, and 95 meters above its surroundings. The castle extended 2500 meters from east-to-west and 362 meters from north-to-south. It is uncertain when this location was fortified. According legend, it was constructed by
Ogata Koreyoshi in 1185, and was gifted to
Minamoto no Yoshitsune to be a stronghold against his brother,
Minamoto no Yoritomo. After the death of Yoshitsune, the Ogata clan was exiled and their territories given to the
Ōtomo clan, who has been sent as
shugo of the province by the
Kamakura shogunate. Shiga Sadatomo, from one of the three major cadet branches of the Ōtomo clan, expanded the fortifications in 1334 and renamed it "Oka Castle". On the other hand, the Bungo no Kunishi states that the Shiga clan entered this area only after 1364 and make Kimure Castle their stronghold, with no mention of Oka Castle, so this history remains uncertain. Many of the buildings in the castle were destroyed by fire in 1771, which had originated in the
castle town. Following the
Meiji restoration, the castle structures were all destroyed by 1873 and the site was abandoned. The composer
Rentarō Taki was inspired by the ruins to write the song
Kōjō no Tsuki, which became famous by being included in the required curriculum for junior high school students in 1901 (although the lyrics were actually referring to
Aizuwakamatsu Castle instead of Oka Castle. The castle ruins are now a historic park. It is located a 25-minute walk from
Bungo-Taketa Station on the
JR Kyushu Hōhi Main Line. ==Gallery==