Yunotai Onsen Kasenjiki no Yu

A wild spring that bubbles up directly from the gravel bank of the Amano River in Kamikuni, with no facilities, no enclosure, and no staff. The water is one of the rarer types around, a carbon dioxide spring, which means it emerges fizzing and effervescent at around 35°C, looking clear but carrying a distinct iron and metallic mineral taste. The low temperature makes it more of a warm soak than a hot bath, but the sensation of carbonated water on skin and the sheer rawness of the setting make it worth seeking out.