It is supposed that this story had gradually changed into a legend, and as the people's knowledge of the Ainu in Ezo (Hokkaido) was gradually deepened, the people had come to believed that Yoshitsune escaped danger at Koromogawa and went over to Ezo to become the king of the Ainu.
このような説話が、のちに語り手たちの蝦夷地（北海道）のアイヌに対する知識が深まるにつれて、衣川で難を逃れた義経が蝦夷地に渡ってアイヌの王となった、という伝説に転化したと考えられる。