Leo the lion cub, destined to be the future emperor of the African jungle, is sent to live with a young Japanese boy named Kenichi. While living among humans, Leo gains various experiences and somehow always manages to get into a bit of trouble. However, when a rat arrives—delivered by a stork, like a little bundle of joy—with a message from home, Leo realizes it is time to return to the jungle. As he sets out on his greatest adventure yet, he remains unaware of the great battles that await him.