Naha Airport is the main gateway, with frequent domestic flights from Tokyo (2.5 hours), Osaka, Fukuoka, and other major Japanese cities. Several international routes connect to Taipei, Seoul, Shanghai, and Hong Kong.
From the airport, the Yui Rail monorail runs into central Naha in about 15 minutes. Car rental counters are at the airport and this is the practical choice if you plan to explore beyond Naha -- public transport outside the city is limited. Ferries connect Naha to mainland Japan (Kagoshima) and to the outer Ryukyu Islands, though these are slow and mainly used for island-hopping rather than arriving from the mainland.