Private onsen in Sounkyo Onsen
A bath you have to yourself: no other bathers, and usually no tattoo problem either.
Is there a mixed onsen in Sounkyo Onsen?
Not one we have found. Mixed bathing (konyoku) survives at mountain, riverside and seaside baths, and we have not recorded one in Sounkyo Onsen. If what you want is to bathe together as a couple or a family, a private onsen is usually how it is done in Japan: the 1 below has a bath your group uses alone. Where Japan’s mixed baths are, and what to wear