Ajikanko Hotel Uminoyadori

The two rotenburo here are named for the clans that fought nearby in the Genpei War: Genji-no-yu (源氏の湯), a half-open-air rock bath with its own cold plunge, best suited to the cooler months, and Heike-no-yu (平家の湯), a fully open-air rock bath looking straight out over the Seto Inland Sea with clear night skies over the peninsula. The two swap between men and women through the day, and there's a separate indoor bath as well. The water is soft and smooth on the skin, said to keep you warm long after you get out. Uminoyadori sits on the Aji Peninsula, at Shikoku's northernmost point, on a quiet stretch of coast with little else nearby. A couple of special guest rooms have their own open-air bath, sometimes with a jacuzzi, looking over the sea or the green of the peninsula.