The story follows four teenagers, Mikoto, Tikari, Yuna and Kate. They all live on a planet called Auralia, there's another planet in the sky above theirs. This planet's name is Zagor. Auralia and Zagor are connected by a huge pipe. This pipe is named Enigma and was built by the humans who used to live on Zagor wich has been deserted many years ago.

 

The reason no one lives on the deserted planet is because of an apocalypse by the species Bariokos. The Bariokos are said to come from experiments that the Zagorian government are rumoured to have executed on human-beings. The Bariokos are a stronger human-race that lacks empathy as well as kindness and mainly operates by the urge to destroy.

 

Mikoto lost his father while his parents escaped the planet. His mother told him that his father chose to stay, with the reason. I have to protect my own species...