"There was once"? Don't kill them.
The last king of Ryûkyû was promoted from king subordinate to a samurai subordinate to the shogun to a titled noble subordinate to the emperor during the Meiji Restoration, then lost all his titles after WW2. Okinawans still speak their own language (regarded as a "dialect" in Japan) alongside Japanese (there's a currently airing anime whose gimmick is the fact that the language exists), and while WW2 militarism and later westernization didn't exactly help keep their culture intact, it still survives in part and some efforts are being made to revive parts of it (partially for tourists, but not entirely).