Shiobara Motoyu Onsen Ōidekan

The headline here is the "Sumi no Yu", a bath coloured jet black by iron-rich sulfur water, one of the few genuinely black springs in Japan. Depending on the weather and season the same water can shift through milky white, grey, and pale green, which regulars call the "five-colour bath". Other pools on the property run the usual sulfurous cloudy white. The whole place has a deep-country feel, set in a narrow valley on the original Shiobara spring site.