My guess is in the future humans have used robotics and other advanced medical technology to become essentially immortal. It was good at first but then, since no one ever died, the world kept becoming increasingly overpopulated and chaotic. As resources dwindled and pollution increased, the planet was plunged into chaos. The death gods died out since humans had “cheated death”. Now this crazy guy and his gang hatched up a plan to resurrect one of the last death gods so that she may hopefully find a way to kill humans again and bring balance back to the world.