It had come to be used as the diplomatic title of the Muromachi shogun since Yoshimitsu ASHIKAGA, the third shogun of Muromachi shogunate government, was appointed king of Japan under a seal of investiture of a title of 'Nihon-kokuo Gen Dogi' by the emperor of the Ming dynasty.
室町幕府3代将軍足利義満が、明皇帝から「日本国王源道義（にほんこくおうげんどうぎ）」の封号を与えられ、日本国王に冊封されて以降、室町将軍の外交称号として使用された。