In 2387 the planet Maris, a Second Earth, is attacked by the Noza Empire. The Nozas need Maris to lay the seeds of their next generation, before the current generation perishes. However, they are unaware of three pistols of immense power, capable of eliminating the Nozas. These weapons are discovered by Maris colonists and dubbed the Zillion weapon system, named for the ancient civilization that created them. Powered by an element dubbed Zillium that is contained in power packs, the energy from these strange yet powerful weapons can engulf and disintegrate even an armored Noza. A trio is formed to wield the Zillion guns and fight back: the White Knights.