Sō clan
Historians consider the Sō clan to have been an offshoot of the Koremune clan (惟宗氏), who served as local officials of Dazaifu and Tsushima Province. The earliest evidence of Sō clan cohesion arises in the 11th century. The Koremune had their start as governors of Tsushima following an incident in 1246, when the Abiru clan, local district officials ("zaichōkanjin") on Tsushima, rebelled against the Chinzei Bugyō and the Dazaifu government which governed all of Kyūshū and the surrounding regions on behalf of the Kamakura shogunate. Dazaifu ordered Koremune Shigehisa to stop the rebellion and to destroy the Abiru clan. He was rewarded for his victory with the post of "Jito" (local land steward), by the Shōni clan, "shugo" (governors) of Tsushima.