On April 6th 1590, Toyotomi Hideyoshi who built a base in Hakone Sounji temple, ordered to built a castle in Kasagakeyama. Then he made his people cut down the tree around the mountain, and moved his base on June 26th. The construction of this castle took only 82 days, and it appeared as if it was built in one night, so it became to be called “Ishigakiyama Ichiyajyo (a castle built in one night)”.