FOR THOSE OF YOU WHO AREN’T FAMILIAR, Japanese people like to get naked and take baths together…in public. No biggie.
Most people call it “Onsen.” Onsen has a long and storied past that I do not have enough time to summarize, but most people attribute public bathing in Japan to two factors 1) the popularization of Buddhist purification rituals, combined with a large number of available natural hot spring sources, and 2) post-World War II Japan had a lack of private bathing facilities. I’m going to personally advocate for #2 as a bigger influencer in recent times (at least in urban areas anyway).