Sanuma Castle was established some time between 1185 and 1187 by Terui Takanao, a close aide of Fujiwara no Hidehara. After the collapse of the Fujiwara clan, Sanuma Castle came under the control of Kasai, a subordinate warrior of Minamoto no Yorimoto. However, in later years, the castle was a residence of Ishikawa, a retainer of the Osaki clan.
Sanuma Castle is also known as Shishiga Castle, because deer were buried here in the past as a form of protection. The castle is a natural fortress protected by swamp and river. Today, the Hon-maru (main building) has become the Shishiga Castle park. In the past, to the southwest of Ni-no-maru, there used to be a swamp called Tai Numa, which made a natural moat to protect the castle. Along the eastern side of the Hon-maru ruins, flows the Hazawa River, which also formed a natural moat.
Also in the vicinity stands Izumo Shrine's Teruhi Kengen. Near this shrine is the Sanuma Memorial Tablet, which is a record of the castle. Earthworks can be seen at the edge of the castle, giving a hint of the former castle.