What have the Idaten been doing in the eight hundred years without any demons to fight? Where do they come from? What is their true nature? And what are they going to do when Dr. Obami plots their defeat?

Rin is intent on wiping out the demons, but without a plan, it'd be too easy for some to escape. With that in mind, Ysley contacts another Idaten named Prontea to formulate a strategy, while the demons begin their own divide-and-conquer campaign against their divine enemies.