User:Plutonium0

guess
It looks like Ceres Fauna and Nanashi Mumei consider each other as enemy because their concept is Nature ( ceres fauna ) and Civilizaton ( nanashi mumei ), in simple sentence ,

Nanashi Mumei ( Civilization ) pollutes Ceres Fauna ( Nature ) and destroys environment.

Ceres Fauna will be destroyed by Nanashi Mumei

( in easy sentence, human civilization is destroying nature )