The rich diet of Okinawans makes this place such an interesting thing to see. Colorful vegetables and fruits, cakes for all occasions and any kind of edible things you can name fill the huge indoor market.
"okinawan staple - pork"
Okinawans know how to cook pork. Try "so-ki soba" in local noodle restaurants: Slow cooked pork ribs on top of local style noodle soup. Some study said that it is for the pork eating habits that Okinawans outlive most other Japanese.
"fish market and the restaurants above"
I didn't try it myself due to lack of free time, but you can buy your fish in the market and pay the restaurant above to prepare it to your liking for lunch. Usually US$5 per person, with rice and soup included.