The planet Lumina Valo and Kurai Varjo were born on.
Far into the future, Vulpes is a pale blue dot not unlike ours. In many ways, it shares similarities with the Earth of the primary timeline- most notably, sharing the same present year. However, it differs significantly in terms of history. This history begins with the K’uminhyō coming to Vulpes, and creating celestial witches, who often were featured in future myths.
Their infamy came to a head in the early 20th century when Imperial Japan- whose K’uminhyō population was significantly higher than the rest of the world- noticed these powerful creatures and saw fit to weaponize them. This unseen military advantage allowed them to pulverize all resistance- eventually taking half of Russia and almost all of Asia. Meanwhile, on the other side of Russia, Finland was battling what remained of the bereaved nation in an earlier form of the Winter War. Eventually, only a sliver of the original territory would be left, and it would remain that way until the present day. Because Finland and Japan became neighbors in a roundabout way, their cultures began to meld together, and their politics did too.
This sharing of values resulted in two very similar societies- conformity being the most important virtue of all, crime being punished remarkably harshly, and military service being compulsory. Another thing that was exchanged between the two countries was the presence of the K’uminhyō. Although still few in number around the globe, the population was concentrated primarily in the territories of these two countries.