山城國
In 784, Kanmu wanted to move the capital away from Heijō-kyō. Tanetsugu recommended the location of Nagaoka-kyō as the spot for the new capital. By the Emperor's command, Tanetsugu inspected the site along with , , , , and Sakanoue no Karitamaro. Later that year, Tanetsugu was put in charge of the construction of the new capital. His appointment may have had the backing of his mother's family, the Hata clan, whose base of operations in Yamashiro Province was near the new capital site. Several members of the Hata clan were later promoted into the aristocracy based on their meritorious service in the construction.