In June, 1398, he was appointed to take over the Shogunal Deputy post from Yoshimasa SHIBA and remained in the post for 6 years until July, 1404, and then Motokuni's post was taken over by Yoshishige SHIBA.
1398年6月には斯波義将の後継として管領に任じられ、1404年7月までの6年間の間を務める、後任は斯波義重。