The story Mao and Kenta belong to was actually inspired by a dream I had. Then I looked to Ao no Exorcist to help me come up with the balance of school life and something supernatural. The story went through numerous revisions and one of them was the idea that the story includes war. I'm still kind of surprised that the story headed in that direction and it makes things more complicated, but I can't see the story progress in any other way.