Nakanoyu Onsen
- Location
- Matsumoto, Nagano, Japan
- Water type
- bicarbonate, sulfurous
- Temperature
- 41 °C
- pH
- 6.5
Water profile
Relaxing — deep, immediate muscle release.
Rich in active gases or metals — a strong mineral character.
Soft water — natural, classic buoyancy.
Nakanoyu Onsen flows with bicarbonate and sulfurous thermal waters, combining the skin-softening alkalinity of carbonate mineral chemistry with the distinctive character of volcanic sulfur, producing a dual-mineral bathing experience long associated in Japanese balneology with well-being. The coexistence of these two mineral types reflects the geological complexity of the volcanic formation through which the spring's water travels before surfacing, where bicarbonate and sulfur deposits from different rock layers mix to create a distinctive and layered mineral profile. Nakanoyu Onsen represents the nuanced mineral craftsmanship of Japan's volcanic hot spring heritage, where the earth's geochemical processes produce waters of remarkable depth and variety.