His first appearance of "Azuma Kagami" (The Mirror of the East) was in the first year of Kenkyu era, the year of 1190, he accompanied MINAMOTO no Yoritomo, the first Shogun of Kamakura bakufu, when he went to Kyoto in an envoy to present Washu (precious eagle feathers) to Emperor Goshirakawa in the same year.
『吾妻鏡』の初見は建久元年（1190年）で、初代将軍源頼朝が鷲羽を後白河天皇に贈る使節を努め、同年の頼朝上洛に供奉している。