Nakoya Onsen
- Location
- Shimada, Shizuoka Prefecture, Japan
- Water type
- bicarbonate
- Temperature
- 40 °C
- pH
- 8
Water profile
Relaxing — deep, immediate muscle release.
Loaded with major ions — the essential minerals (Ca, Mg).
Soft water — natural, classic buoyancy.
Nakoya Onsen is a hot spring in Japan whose bicarbonate mineral waters provide the smooth, skin-softening, and mildly alkaline bathing experience that has made bicarbonate springs one of the most popular and widely distributed therapeutic water types within the Japanese hot spring classification system. The alkalinity of bicarbonate spring water reacts with the proteins and fatty acids of the skin surface in a gentle saponification process, creating the distinctive silky sensation that Japanese bathers describe as slippery or smooth water, an effect prized as evidence of the water's skin-cleansing and beautifying properties. Bicarbonate springs are found throughout Japan's volcanic and mountain zones wherever geothermal water interacts with carbonate-bearing rock formations before reaching the surface, and Nakoya Onsen represents this valued spring type within the broader landscape of Japan's extraordinary geothermal bathing heritage.