Mars (Mitsuteru Yokoyama)

is a Japanese manga series written by Mitsuteru Yokoyama from 1976 to 1977 in Weekly Champion Magazine. A 2-episode OVA directed by Junji Nishimura was released in 1994, while the anime adaptation entitled aired on AT-X which aired from October 31, 200 to February 6, 2003 for 13 episodes.

Plot
On the uninhabited island of Akinoshima, a journalist named Iwakura discovers a young boy in suspended animation inside a South Sea volcano. The boy awakens with no memory whatsoever but happens to have awoken a century earlier before his alien masters plan to use his powers to destroy all of human civilization.

With the future of humanity in the boy's hands, the boy decides to face against the six alien observers and their guardian robots to protect the Earth, or die trying.

New Century Legend Mars
Mars is an amnesiac man discovered on a forming volcano island. In reality, Mars is from outer space, and is supposed to gather information to decide whether Earth should be destroyed or not. Along with the giant robot Gaia, and his mysterious images of a woman urging him not to destroy the world, Mars decides to fight for Earth rather than destroy it, even if it means fighting his own kind. But if Mars is killed, Gaia will explode, destroying Earth along with it.