« Hisui is based on the real-life island of Hokkaido during the Muromachi period, when it was still known as Ezo, with new settlers from other regions interacting with natives in a parallel with the interaction between Hokkaido's Ainu people and Japanese settlers. » wikipedia this is incorrect; the natives are actually disappeared in Legends: Arceus and the people you meet there are just earlier immigrants, which is why they don't actually know the meaning of the lore. the Diamond and Pearl clans ARE those Muromachi-era Japanese settlers

also it's clearly Meiji-era (or just before) the Galaxy Team Headquarters has a fucking Galarian Weezing