man i really needa stop forgetting these title's

anyway i'd appreciate help getting the name of an anime that i havent watched but want to.

from what i remember reading there is a race of animal people and a civil war breaks out bit vague but all i can remember about the actual story line but for as much as it helps i believe the protagonist might have something to do with a waterfall? (might be mixing anime's but i believe it said something to do with how he got to the village with the animal people)

thanks in advance!

edit: remembered a little more about it, if i recall correctly the protagonist had a mask attached to him

also i honestly dont remember clearly if all the information is valid it was a looong time ago i read about it XD

thats the one thanks!