曹Bicarbonate
A sodium bicarbonate spring of the classic jūsō-sen style, weakly alkaline and soft on the skin. The on-site notice describes the water as smoothing and silky underfoot — squarely in Japan's beauty-water family. The source emerges lukewarm at 35.4 °C so the bath is reheated for comfort, but otherwise it runs as a free-flowing, undiluted source with no recirculation or disinfection.
Good for
Smooth skin
Bicarbonate and alkalinity gently lift dead keratin while silica hydrates, leaving skin smooth. This is the basis of the beautifying-water (bijin-no-yu 美人の湯) reputation.
dry, rough skin
Recovery
Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.
fatigue, stress
Measured at the source
Source temperature
35.4°C
Warm
Tonicity
Hypotonic
Evidence
- Maeda M. 温泉の医学的効果とその科学的根拠. J. Hot Spring Science 70:197–207, 2021.
- Naito Y et al. A Hot-Spring Water Improves Inflammatory Conditions in an Atopic Dermatitis Model. Biomedicines 13(11):2707, 2025.
- Li H et al. Bicarbonate Ionized Water Bathing Enhances Natural Killer Cell Activity. Scientific Reports 14:51851, 2024.
- Takeda M et al. Hot spring bathing practices have a positive effect on mental health in Japan. Heliyon 9(9):e19631, 2023.