Site of the Wada Fort 和田城跡（和田砦跡）

During the Sengoku period, the daimyo had little power over Koka, which was unusual at the time. The area was governed by local groups based on blood and territorial ties, and they adhered to an autonomous structure of regional governance. In the later years of the Sengoku period, these local groups established the Koka Gunchuso. This self-governing organization, along with the collective defense strategy of the region, was crucial in maintaining stability and preventing the rise of a single dominant power.

The ninja forts were built at places that allowed intruders to be monitored. The Wada Fort was constructed on a hill at the end of a valley and offered a panorama of the surrounding area. Each side of the square main enclosure measured 50 meters and was surrounded by earthen walls, some of which are believed to have reached up to 7 meters in height.

The valley once had seven forts, all at good vantage points. Intruders entering the valley were under constant surveillance, and any suspicious movement would trigger an attack.

The Wada family lived in the area during the Sengoku period and built the forts in the valley. They were retainers of the Rokkaku family, who oversaw southern Omi Province (present-day Koka). Wada Koremasa (1536–1571), one of the most prominent family members, supported the influential warlord Oda Nobunaga (1534–1582) and played a major role in convincing other Koka ninja to do the same. Nobunaga was instrumental in restoring a stable government and establishing conditions under which the unification of Japan eventually became possible.