A new onsen opened at Aj Resort on Ikei-jima in Uruma (connected to main island by bridge) this past spring! The bath facility is called 黒潮の湯 Kuroshio-no-yu. It is not huge, but it is nice, with an indoor and outdoor bath, as well as a family bath! So while those with tattoo cannot use the public onsen (unless their policies have changed), there are really nice looking private family/couple baths that can be booked for 90 minutes for only 3000yen (they request booking in advance for the private baths since they only have 2 available private baths!). Green tea is added to the Okinawa deep-sea water, and the outdoor bath has jets.
The entrance fee is 1,200円 for adult non-overnight guests.
The only downside is it does not look like they offer any extra spa services. It is also quite a ways to get there as you have to cross the bridges from Uruma to Henza, Miyagi, and then finally all the way to the tip of Ikei-jima! So the journey is quite long to get out there… but it is quiet and remote, so you can have a peaceful, relaxing experience.
Since I was completely by myself when I went, I was able to snap some photos (a rare occasion for onsen!).
Aj Resort Onsen: 〒904‐2421 沖縄県うるま市与那城伊計1286