Keep Okinawa in mind if your ever looking to get some subtropical island exposure!
This bears repeating.
Especially right now...
Best seasons are fall/winter/spring..and we ride year round, with most crowds visiting in winter, to escape the colder mainland.
... after it has been forecast that this winter (2013/2014) is going to be a bit on the cold side, due to a larger (deeper?) than usual high pressure area building up over northern Asia and the Arctic. Cold is relative: it means that temperatures on the islands in Okinawa should be around 15C, lower in the north, higher in the south, and, most importantly, we'll have many days with steady northeasterly wind (wind speeds are typically 10-20m/s = 35-70km/h).
Islands to look for are - from north to south - Okinawa Island, Miyako Island, the Yaeyama Islands (airport on Ishigaki Island, suitable beaches mostly on the lagoon islands nearby: Taketomi, Kohama, Kuroshima).
Add to this weather the fact that there are more airlines flying to Okinawa than ever before and they are competing for your ticket dollars. Especially airfares to Miyako and Ishigaki have come down dramatically (with Ishigaki opening a new airport in March, more airlines are flying in, and fares are now less than half of what they were just a year ago).
Like Kaito (on Okinawa Island), yours truly (on Ishigaki Island) can also be reached by PM for more info.