Kōchi-jō is one of just a dozen castles in Japan to have survived with its original tenshu-kaku (keep) intact. The castle was originally built during the first decade of the 17th century by Yamanouchi Katsutoyo, who was appointed daimyō by Tokugawa Ieyasu after he fought on the victorious Tokugawa side in the Battle of Sekigahara in 1600. A major fire destroyed much of the original structure in 1727; the castle was largely rebuilt between 1748 and 1753.
The castle was the product of an age of peace – it never came under attack and for the remainder of the Tokugawa period it was more like a stately home than a military fortress. The fee is for entry to the castle itself; it's free to walk in the surrounding grounds.