Rurikei Onsen

A brand new super sento complex about an hour to an hour and a half by car from Osaka, with konyoku (swimsuit required), a pool and kids' play areas (included in the onsen price), a restaurant, ganbanyoku, and rice bran burial (couldn't try it — fully booked today). There's a separate kashikiri bath in a separate building, and nearby there's a campsite, hotel, BBQ, illumination, and a great free playground. In the men-only zone: washing area with shampoos, jet bath (40°C), radon bath (42°C), three or four barrel baths (41°C, barrels are covered but in an unheated area), sauna where you can ladle water onto the stones yourself (though the sauna wasn't very hot — thermometer under the ceiling showed 90°C but down below it was barely warm), mizuburo (16°C). In the shared indoor zone: radon and "mildly radioactive" baths (about 41°C, and quite deep — waist-level), plus reclining baths. Outside there are 4 small varied rotenburo (2-4 person capacity, 41°C) and about five barrel baths (40°C). The complex is large, new (opened in 2025, less than a year ago), and varied, which is attractive. Though without the radon signs, the baths aren't particularly noteworthy. Today it was packed with families with small kids (because of the play areas, pool with inflatable rings, and it being a day off). A plus is that it's noticeably high up and about 5 degrees cooler than Osaka (the car showed 0°C and there was a bit of snow around), so in summer you can come here to escape the heat.