The Kaneda castle, which once stood on Jou-yama's 270m tall summit, was built, it is said, in Korean style. We're not sure exactly what that means, especially since the castle is completely gone now, and the ruins that can be seen today are of a WW2 artillery installation. The most interesting thing that still remains is the wall that once surrounded the castle. The wall wraps around the mountain and is several km long and about 5m high - a major piece of work. Perhaps the Korean style of doing things was putting fortresses on remote, steep peaks and surrounding them with substantial defenses. The Japanese castle, in comparison, seems to be just a spiffed up palace for the residing lord, situated on a comfortable, small hill in the middle of a city, and rather lacking in defenses. Indeed, historically Japan's military conflicts tended to involve battles fought far away from the centers of control and once a battle was lost, there was usually nowhere defensible to run to and hole up for the loser (they were usually killed outright or managed to hide for a while in the mountains). This was, incidentally, also true for Japan in WW2, as the Japanese archipelago remained undefended while its navy overextended itself all over the Pacific Ocean.