Because it's all set in fantasy pre-Samurai NOT-Japan.
In an era where the emperor has some power and is less ceremonial.
It talks about how a foreign Yogoan emperor took over, and how his descendents still rule.
It talks about how local animist rituals and customs remain, but only in part, as despite their small size compared to the native population the Yogoans wielded considerable influence over the people.
This includes eradicating certain animal species.
The whole message was basically "progress" at the cost of the "Old Ways."