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While some tech hasn't reached Ransei, such as Pokeballs or Pokemon Center-style healing technology, and the characters are based on feudal Japanese figures, Ransei takes place in modern times. There are factories, computers, airships, even Mewtwo.
Hisui is based on Hokkaido back when it was called Ezo, which is a stretch to call "ancient" Japan. Kimono are present as a lot of Japanese including the settlers of Ezo wore kimono up until the early 1900s.
