Sō clan
Though now holding the hereditary post of "shugo" of Tsushima, the clan remained vassals of the Shōni until the late 15th century. In the course of breaking away from the Shōni clan, the Sō clan started to claim that it originated with a grandson of Taira no Tomomori, Taira no Tomomune. The Sō clan moved its base from northern Kyūshū to Tsushima around 1408. Although it struggled to keep its territory in Chikuzen on Kyūshū, the clan was finally purged from that region by the Ōuchi clan in the mid-15th century.