Japanese invaded Okinawa in 1609 as part of an expansion not unlike our expansion West in the late 1800s. Two hundred and seventy years later Oki became a Prefecture and had been fully integrated into Japan. Not sure what vote you are referring to.
I spoke with my friend further on the matter as his mom passed away some years ago. The vote was about whether Okinawa would continue being governed by the USA or by Japan.
He said that Japan launched an intensive public relations campaign which included getting native Hawaiians to do commercials describing how everything in Hawaii sucked when America took it over. The older people of Okinawa were in favor of continuing under USA governance, while the younger people, who did not remember the brutality of Japanese control, voted in favor of being governed by Japan.
He says Japan's public relations campaign occurred in the early 1970s.
This is what I found on the matter.
https://en.wikipedia.org/wiki/1971_Okinawa_Reversion_Agreement