Test pilots George Minami and Hiromi Amachi, along with Andro Umeda and Mutan, two alien beings from the planet Sanno, rid the dying Earth from the threat of the "Waldaster" and continue to research the "Leap Flight Engine" to reach a new home for humanity.

In the 21st century, humanity is searching for a "Second Earth" to colonize. The exploration ship "Space Angel" is attacked and destroyed by the Waldarians, a group of warlike aliens. To fight against this threat, Professor Souzou Amachi develops a method to transform an ordinary human into an indestructible armor-clad "Space Knight". The human in question is the hot-headed young space pilot Joji Minami, who wants to avenge the death of his father at the hands of the Waldarians.—Dimos I