On the other hand, there is a theory, which is based on the theory of Yoshimitsu ASHIKAGA equals the King of Japan, that Ieyasu TOKUGAWA saw the advantage of its authority, and changed himself from Fujiwara cognomen to Minamoto cognomen, obtaining power equivalent to that of the King of Japan by becoming both seii taishogun (literally, great general who subdues the barbarians) and Genji choja and used such power for controlling both court nobles and samurai families (Tomohiko OKANO).
一方、徳川家康はその権威に着目し、藤原姓を源姓に改め征夷大将軍と源氏長者を一身に兼ねることにより日本国王に相当する権威を手に入れて公家と武家の掌握に利用した、という足利義満＝日本国王論に依拠した説がある（岡野友彦）。