The world is in ruins thanks to a variety of creatures called Arigami. While they are somewhat demonic or mythic in appearance, each one is actually made up of thousands of single-cell organisms. Basically, they look cool, but given this is a sci-fi game they have some nonsense about why they’re not just monsters. In order to eradicate these creatures, the various scientists and mysterious powers that be recruit God Eaters, people with the ability to break down the bonds of the Arigami.