The story is set in the year 2050 AD, and mankind has been steadily advancing its space technology. However, the planet is suddenly set upon by a mysterious enemy: the forces of Eldar, who came from 250 years in the future. In their time, 2300 AD, their planet Eldar was invaded by Earth, and soundly defeated by Earth's Trinity Energy, a mysterious energy used in their weaponry that possesses power many times that of a hydrogen bomb. The Eldar people's objective is to steal this Trinity Energy before it can be used against them. The Eldar forces begin by taking over Jupiter's moon Io, one of the places humanity has immigrated to by then. After that, they begin to attack Trinity City with their legions of Cosmosauruses in order to steal the Trinity Energy. Toshiya and his friends use God Sigma to protect the planet and the Trinity Energy, and the battle evolves into a long war to retake Io. (Source: Wikipedia)

Leo (a.k.a. Kimba in the U.S.) is a young ambitious lion cub who takes his father's place as emperor of the jungle when is father is killed by poachers. Even though his father's fate was met by the hands of humans, Leo is one of the few animals in the Jungle that doesn't fear or feel hatred toward humans. He is not alone either, he is guided by friends of his father to help create the best animal kingdom there can be. (Source: ANN)

Jungle Emperor was such a hit in Japan, that Dr. Tezuka went ahead and produced a sequel in 1966, known in Japan as "The New Jungle Emperor" or "Onward, Leo!" The trouble (for us in the rest of the world) was that he made the series without having a deal with NBC, and he made it more like his original manga story, which means that there were a lot of characters that died and some of the episodes could be depressing. NBC thought that there was no way they could sell that kind of show, and they were quite happy with the 52 episodes they had, so the New Jungle Emperor series wasn`t seen in this country until 1984, when it was given the title Leo The Lion. This series was supposed to take place a few years after the original Kimba series. Kimba was an adult, with Kitty as his mate, and they had two cubs. Most of all this series was the story of Rune, the male cub, as he grew and learned to be as strong as his father. For legal reasons, the producers of the English-dubbed version could not use the name Kimba, so they used the original Japanese names for all the characters. (Source: Official Website)