Many centuries ago, in the distant mists of ancient time, a disaster shook the Earth. The skies were charred with fiery blasts, and poisonous rivers flowed throughout the continents. Human beings, who once gazed upon glorious skies and breathed pure air, were forced to find a way to survive. They found that way under their feet... under the ground.

Sheldar became the capital city of the underground world. In their subterranean existence, the era of machines passed them by. Perhaps the people even forgot what the sky looked like....

Ryu, a member of the Sheldar Rangers, witnessed a mysterious event while checking out a Bio-chem company facility during a routine patrol.

Thus begins the story of Deep Earth....