A gentle simple thermal spring that punches above its class on silica: 188 mg/kg of metasilicic acid, enough to leave the thin, moisturizing film that makes skin feel noticeably smoother afterwards. Mildly alkaline and soft on the skin, it sits squarely in Japan's beauty-water family, while the light overall mineralization (575 mg/kg dissolved solids) keeps it undemanding for a long soak. At the source the water carries a very faint yellow tint but stays clear, with no taste and almost no smell. The property's guest sheet notes a private open-air bath on the third floor, usable without a reservation for up to 60 minutes.
Good for
Aches & joints
Warmth eases stiffness and raises the pain threshold. Radon and sulfate springs show the strongest evidence for joint and muscle pain.
stiff shoulders
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
Full composition
The bar is each ion's share of charge (mval%) within its group; over 20% names the spring. Gases, silica and trace metals are measured by mass only.
- Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺94.4mgP27 national79%
- Potassiumminor; matters for drinking limitsK⁺19.1mgP61 national9%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺6.5mgP19 national6%
- Magnesiummild; a laxative if you drink itMg²⁺3.4mgP40 national5%
- LithiumLi⁺0.20mgP38 national0.6%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻167mgP54 national54%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻54.2mgP28 national30%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻37.5mgP36 national15%
- Hydrogen phosphateHPO₄²⁻1.4mgP86 national0.6%
- FluorideF⁻0.40mgP29 national0.4%
- BromideBr⁻0.20mgP29 national0.0%
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃188mgP83 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂2.7mgP23 national
- H2SO4FreeH2SO4Free0.0000mg
- Phosphoric acidH₃PO₄0.0000mg
- Metaarsenious acidHAsO₂0.0000mg
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂13.2mgP45 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S0.0000mg
- ArsenicAs0.04mgP47 national
- CadmiumCd< —mg
- CopperCu< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —mg
- LeadPb< —mg
Measured at the source
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.
- Donaubauer AJ et al. Serial radon spa therapy on pain in musculoskeletal disorders. Frontiers in Immunology, 2024.
- Verhagen AP et al. Balneotherapy for rheumatoid arthritis. Cochrane Database of Systematic Reviews CD000518, 2015.
- 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.