A long time ago, the humans of the Neraland erected a magnificent tower in order to show their highest respect to the Goddess Nera. Moved by the devotion of the people, the goddess opened a door to the other world at the top of the tower. The feathered people from the other world brought culture and progress to mankind, but in the end the two races fought against each other in various conflicts. Hundreds of years have passed since the war, and the continent is once again shrouded in a dark cloud of unease and weirdness...

(Source: Bilibili)