from what was said, i gather the "humans are food" bit only comes once the madness wears off. Kou, Dakugaku, Lirin and Yaone have all had enough will power yp withstand it. Kou only "gave in" because of Jianyi's experiments and torture, but he beat it instead of having it runs it's course. The way they talk about human/demon relationships before, I gather it's a new mindset that didn't exist(at least not widescale) before.