There is a great possibility that the original story of Urashima Monogatari in the 8th century, which can be seen in "Yuryaku-ki," "Tango no kuni Fudoki," and the ninth volume of "Manyoshu" among other sources, was written by IYOBE no Umakai as a bizarre novel based on concepts of Taoist immortality.
『雄略記』や『丹後国風土記』、『万葉集』「巻九」などに見られる8世紀の浦島物語の原話は伊預部馬養によって描かれた神仙伝奇小説であった可能性が大きい。