When I was living in Sasebo, I would go to the Onsen in Hius Ten Bosch every Sunday. They had three baths, one super hot, a less hot, and a outdoor bath. I would spend 1 to 2 hours rotating between the three. After I would relax in the tatami room. Sometimes I would take a nap in there. It was so relaxing and refreching. I miss my onsen
. They have some in Okinawa, but I havn't tried any of them.
I have heard of onsens not letting people in with tatoos. I have one tatoo on my shoulder, I usally don't tell them. However if I had large tatoos or exposed tatoos I am sure it would be a problem.