Private onsen in Nagasaki

Is there a mixed onsen in Nagasaki?

Not one we have found. Mixed bathing (konyoku) survives at mountain, riverside and seaside baths, and we have not recorded one in Nagasaki. 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 4 below have a bath your group uses alone. Where Japan’s mixed baths are, and what to wear