A sulfur spring rising at 67.8 °C from wells on the ryokan's own grounds in Beppu's Kannawa district — among Japan's hottest natural sources. The posting names it a sulfur and bicarbonate water: hydrogen sulfide and thiosulfate ions sit alongside a strongly bicarbonate-led anion profile, giving the sulfur family's character with a bicarbonate softness layered in. At pH 6.4 it is neutral and only lightly mineralized — the printed ion tables total roughly 380 mg/kg — so the touch is gentle rather than sharp. The panel documents the water for chronic skin conditions, cuts, cold sensitivity and fatigue recovery.
Good for
Skin conditions
Sulfur and acidic waters are antibacterial and keratolytic, studied for atopic dermatitis and psoriasis.
atopic skin, eczema
Circulation
Skin-absorbed CO₂ and hydrogen sulfide relax the vessel walls; carbon-dioxide springs can raise peripheral blood flow several-fold.
tired legs
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
Cuts
Mineral-rich chloride, sulfate and sulfur waters have a long-recorded soothing effect on minor cuts and slow-healing skin.
minor wounds
Recovery
Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.
fatigue, stress
Take care
Sensitive-skin caution
Strongly acidic or sulfur-rich water can sting broken, atopic-flare, or dry elderly skin. Ease in slowly and rinse off if it stings.
broken or dry skin
- Acute illness (especially with fever)
- Active tuberculosis
- Malignant tumor
- Severe heart disease
- Respiratory failure
- Renal failure
- Bleeding disorders
- Severe anemia
- Any other illness in an actively progressing stage
- Pregnancy (especially early and late stages)
- Dry skin in the elderly
- During episodes of diarrhea
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⁺62.1mgP16 national57%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺28.1mgP46 national30%
- Magnesiummild; a laxative if you drink itMg²⁺3.6mgP42 national6%
- Potassiumminor; matters for drinking limitsK⁺11.5mgP48 national6%
- ManganeseMn²⁺0.70mgP77 national0.6%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻195mgP56 national63%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻44.5mgP41 national18%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻32.4mgP24 national18%
- NitrateNO₃⁻1.0mgP82 national0.4%
- Hydrogen phosphateHPO₄²⁻0.60mgP75 national0.2%
- Hydrogen sulfideHS⁻0.40mgP51 national0.2%
- FluorideF⁻0.10mgP9 national0.2%
- ThiosulfateS₂O₃²⁻0.20mgP52 national0.0%
Measured at the source
On the certificate
- Chronic digestive disorders
- Diabetes
- Hypertension
- Cold sensitivity
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.
- Tei C, Kihara T. Waon Therapy for Chronic Heart Failure. J. Cardiology 53(2):214–218, 2009.
- Coavoy-Sánchez SA et al. Hydrogen sulfide and dermatological diseases. Int. J. Dermatology, 2019.
- Naito Y et al. A Hot-Spring Water Improves Inflammatory Conditions in an Atopic Dermatitis Model. Biomedicines 13(11):2707, 2025.
- Akiyama H et al. Antimicrobial effects of acidic hot-spring water on S. aureus. J. Dermatological Science 24(3):193–200, 2000.
- Toriyama T et al. Carbon dioxide foot bathing on critical limb ischemia. International Angiology 21(4):367–373, 2002.
- 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.
- Ministry of the Environment, Japan. 禁忌症及び入浴又は飲用上の注意事項 (2014 notice).official