Ryuu stows away on a space vessel, only to be found by the crew when it's far to late to return to Earth. So they stick him in a spare sleep capsule instead. Things take a turn for the unexpected, however, when Ryuu wakes up to find himself the sole survivor of the expedition, the spaceship having crash landed on a grossly mutated and wholly unfamiliar Earth.

Joining forces with fellow survivors from a different crash, Ryuu and his comrades fight to survive on this new and deadly Earth as they search for any humans that might have made it through the mysterious apocalypse.

(Source: MU)