[3][4] Kitsuki Castle is located on Shiroyama hill on the southern seashore of the Kunisaki Peninsula in Kyushu in what was once northern Bungo Province.

Its elevation is only between 20 and 30 meters, but as the slopes of the hill are steep cliffs and the site was seen to be protected on either side by the Yasaka-gawa and Takayama-gawa rivers, the location was considered a natural fortress.

In the Sengoku period, Kitsuki Shigenao was an important retainer of Ōtomo Sōrin, who directly or indirectly controlled northern half of Kyushu.

However, the Ōtomo were defeated by the aggressive Shimazu clan in a series of battles in Hyūga Province, losing most of the territory and many of their retainers, including their capital of Funai (modern-day Ōita city) in 1587.

Simultaneously, Tadazane's younger brother Ogasawara Tadatomo, who had been a hatamoto, was given Kitsuki Castle and its surroundings with a kokudaka of 40,000 koku, making him a daimyō.

The general area of Kitsuki retains the look of a traditional castle town with a many surviving samurai houses guarded by stone walls and fences, which draws many tourists.