In the Wada War of 1213, Yasutoki, along with his father, Yoshitoki beat down Yoshimori WADA and, due to his distinguished service in the war, was appointed as the steward in charge of a lord's manor of Enda County, Mutsu Province.
建暦3年（1213年）の和田合戦では父・義時と共に和田義盛を滅ぼし、戦功により陸奥国遠田郡の地頭職に任じられた。