On a recent concert tour in Japan, I had the chance to visit several thermal baths and to chat with people about the tradition of bathing. I was fascinated by their differences with American spas.

A cornerstone of Japanese culture, onsen runs the gamut—but these experiences take hot-spring soaks to a whole new level.

Japan's “hot spring capital” is trying to find ways to make one of the country's most popular pastimes more inclusive for people who identify as LGBT, when most public baths are segregated according ...