Originally situated atop a small island that connected to the mainland by a sandbar at low tide, Usuki Castle is now in the middle of the town.
It was built by Otomo Sorin in 1562 who moved here from Funai Castle a little north. It's position was much better for defense and he left his son in charge of Funai castle.
The Shimazu attacked the fortress aided by a troop of Buddhist monks. Sorin had become Christian and the Buddhist monks sacked and burned all Christian churches in retaliation for the destruction of their temples in the area. Sorin used a cannon against the Shimazu, possible the first time a cannon had been used to defend a castle in Japan., but was eventually defeated though first all the Christians in the castle had been evacuated by Portugese ships.
In 1873 the castle was decommissioned and almost all structures dismantled and a few years later the castle easily fell to Saigo Takamori. The main gate was rebuilt in 2001.