Manga: Aesop's Tale(1983)

Manga Aesop Monogatari

Aesop is a trouble-making young boy who finds himself in another world filled with creatures he never believed to exist, such as fairies and talking donkeys. He sets off to find a way back to the normal world. On his journey he befriends many classical creatures from well-known fables and encounters many trials, each teaching him a valuable lesson.

(Source: Anime News Network)