琉球族
The Ryukyuan languages were once widely spoken throughout the Ryukyu Islands, but saw a decline in speakers as a result of assimilation policies during much of pre-WW2 Japan. This event caused the Ryukyuan people to experience a language shift towards Japanese. In the Okinawa Islands specifically, many learners of Japanese spoke it with a substrate from the Okinawan languages, causing a distinct variety of Standard Japanese to form, known as Okinawan Japanese.