This is because of such a background that the conquest of three Korean countries by Jinguu Empress was believed as a truth and that Japanese who lived in an island country (except priests or merchants who had a chance to meet foreigners) were less conscious on abroad for a long time, as "Soga monogatari" (Myohonji-bon) written in Kamakura Period described western Japan as 'Kikai, Korea and Io-island'.
もっとも、かつては神功皇后の三韓征伐が史実と考えられていたこと、鎌倉時代の『曾我物語』（妙本寺本）においても日本の西の果てを「鬼界・高麗・硫黄嶋」と記されており、島国に住む日本人（外国と接する機会のある僧侶や商人などの例外を除く）における長年にわたる対外意識の希薄さが背景にあったと考えられている。