Kyushu > Kumamoto > Kurokawa Onsen
A detached inn offering private, free-flowing natural hot springs in every room, renowned for their skin-beautifying benefits.
Ryokan Kounoyu
旅館こうの湯
6784 Manganji, Minami-Oguni machi, Aso-gun, Kumamoto, 869-2402, JAPAN
Phone：+81-(0)967-48-8700
Spring Quality
Sodium, Calcium – Hydrogen carbonate / Sulfate / Chloride springs
ナトリウム・カルシウム―炭酸水素塩・硫酸塩・塩化物泉
(Hypotonic, Neutral, High temperature spring)
Excellent 100% natural free-flowing hot spring
with multiple properties —
for beautiful skin, hydration, warmth, and healing
Hot springs are believed to form when rainwater or snowmelt seeps underground, or when ancient seawater becomes trapped deep within the earth. Heated by magma or the earthʼs internal heat, this water dissolves minerals from underground rocks and slowly rises to the surface over years—or even tens of thousands of years.
Onsen Components
160.9 mg/kg
52.96mval%
■ Helps improve dry skin through its moisturizing effect
■ Relieves muscle tension and alleviates pain
■ Promotes blood circulation, helping to reduce sensitivity to cold
■ Boosts metabolism and supports detoxification
54.0 mg/kg
20.39mval%
■ Supports the formation and regeneration of the skin barrier
■ Helps soothe pain and inflammation
■ Regulates the contraction and dilation of blood vessels
■ Strengthens the skin’s barrier function
288.8 mg/kg
37.01mval%
■ Helps remove old keratin and excess sebum for smoother skin
■ Leaves the skin feeling fresh and refreshed after bathing
■ Washes away impurities, keeping the skin clean
■ Helps improve circulation by dilating blood vessels
■ The main component of Hydrogen carbonate springs, known as one of the “Hot springs for beautiful skin”
197.2 mg/kg
32.10mval%
■ Dilates blood vessels and promotes circulation to the extremities
■ The warming effect from increased blood flow helps regulate the autonomic nervous system
■ Promotes skin metabolism, improving firmness and elasticity
■ Supports recovery from skin issues such as dry skin and minor cuts
■ The main component of Sulfate springs, known as one of the “Hot springs for beautiful skin”
138.7mg/kg
30.59mval%
■ Salt’s bactericidal effect helps treat minor cuts and wounds
■ Salt helps block sweat glands, enhancing heat retention
■ Improved heat retention contributes to balancing the autonomic nervous system
■ A salt coating helps promote moisture retention
397mg/kg
Exceeds the hot spring standard value of 340 mg/kg
■■ Acts like a natural soap, emulsifying dead skin cells and sebum for gentle cleansing
■■ Leaves the skin smooth and well-hydrated after bathing
■■ Provides a refreshing, clean feeling after bathing
■■ A cleansing-type onsen known as “Hot springs for beautiful skin”
This component is formed by the combination of the cation ■Sodium ions (160.9 mg/kg, 7.00 mval, 52.96 mval%) and the anion ■Hydrogen carbonate ions (288.8 mg/kg, 4.73 mval, 37.01 mval%). When present at 340 mg/kg or higher, it qualifies as a hot spring component. Commonly known as baking soda, it emulsifies sebum (breaking oils into fine particles so they mix with water), making it easier to wash away. This process softens dead skin cells and leaves the skin smooth and refined. It is a key component that characterizes “Hot springs for beautiful skin”.
*The bars for Metasilicic acid 50 mg/kg and Metaboric acid 5 mg/kg represent the qualification criteria for hot springs. The number of bars indicates values such as “more than XX times the hot spring standard” or “about XX times the hot spring standard”.
Metasilicic Acid 251.4 mg/kg
■ Natural moisturizing component
■ More than 5 times the hot spring standard (50 mg/kg)
Metaboric Acid 9.7 mg/kg
■ Helps keep the skin clean
■ About 2 times the hot spring standard (5 mg/kg)
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Total Dissolved Substances
(excluding gaseous)
1,180 mg/kg
About 8-11 times more components than standard bath additives!
Hydrogen Ion
Concentration
pH 6.4
Neutral
gentle hot spring watersn
Spring Temperature
60.5 ℃
Maintained at a comfortable temperature by adjusting the water flow
Color of water /
Smell of water
Colorless to Pale green
Faint hydrogen sulfide odor
Volume of water
100~150 liters per minute
(Private hot spring source / Mechanically pumped)
Hot spring water usage per person (spring discharge / maximum capacity)
→ 100~150 / 50 guests ＝ 2~3 liters / per minute
*To meet the requirements for kakenagashi (flowing directly from the source),
at least 1 liter of hot spring water per minute per bather
is required for proper bath management
Status of Source Utilization
| Water added | Heated | Disinfected | Circulated | Bath additives |
|---|---|---|---|---|
| No | No | No | No | No |
*All baths are supplied with 100% natural free-flowing hot spring water
Semi Open-air Bath in the one-story Guest room “Suoh”
All guest rooms have a private open-air bath or semi open-air bath. Keeping the “Kurokawa-ness” atmosphere of being close to nature, the rooms are quieter and offer private time and space where you do not have to worry about anyone else. The semi open-air bath at “Suoh” has a unique “L” shape.
Skin Feeling Gauge
Ideal for:
People seeking beautiful skin
People with dry skin
People concerned about
minor cuts
People feeling stressed
People sensitive to cold
Peopl seseeking a refreshing
sensation after bathing
Indications by Spring Quality
(for bathing)
Cuts
Peripheral circulatory disturbance
Sensitivity to cold
Depression
Dry skin
General Indications (for bathing)
Chronic pains or stiffness of muscles or joints (chronic phase of rheumatoid arthritis, osteoarthritis, lower back pains, nerve pains, frozen shoulder, bruises, sprains, etc.), Muscle stiffness in motor paralysis, Sensitivity to cold, Peripheral circulatory disturbance, Gastrointestinal hypofunction (slow digestion, intestinal gas formation, etc.) Mild hypertension, Impaired glucose tolerance (diabetes), Mild hypercholesterolemia, Mild asthma or Emphysema, Hemorrhoidal pains, Autonomic instability, Various symptoms from stress (sleep disorders, depression, etc.), Restorative phase from illness, Recovery from fatigue, Health promotions
General Contraindications (for bathing)
Active stage of diseases (especially when fever is accompanied), Active tuberculosis, Advanced
malignant tumor or the case of significant debility involving severe anemia, Severe cardiac or lung
diseases involving suffocation feelings with a little movement, Severe kidney diseases involving
edema, Gastrointestinal bleeding, When bleeding is visible, Acute exacerbation stage of chronic
diseases
*There are no general indications or contraindications for drinking.
Onsen Power Chart
Open-air Bath in the maisonette Guest room “Asebi”
The open-air baths in the maisonette-type guest rooms are all rock baths with large, boldly arranged rocks. Guests can bathe while enjoying the seasonal expressions of the trees and the starlit sky that only the clear mountain air can provide. Room “Asebi” has a rock cave and a sleeping bath.
Keywords of this Onsen
Cuts・・・① Cleanses the wound area, ② promotes tissue regeneration, ③ helps disinfect.
Peripheral circulatory disturbance・・・① Regulates metabolism, ② dilates blood vessels, ③ retains heat and promotes peripheral blood flow.
Sensitivity to cold・・・① Conditions the skin and allows heat to penetrate, ② dilates blood vessels and warms the body to the core, ③ seals in warmth with a protective salt layer.
Dry skin・・・① Removes dead skin cells and smooths the skin, ② and ④ provide deep hydration, ③ retains moisture with a protective salt layer.
Depression・・・② Helps regulate the autonomic nervous system, ③ activates the parasympathetic nervous system and relieves mental tension
Large Public Baths for men and women “Mori-no-Yu”
The vast public open-air baths are surrounded by trees, and both the men's and women's baths are spacious enough to accommodate 20 adults. There is also a roof over the baths and a rock cave, allowing visitors to enjoy bathing even when the weather is bad. The washing area is also located in a hut, making it easy to use.
Onsen Classification
️Hot springs are classified not only by their spring quality, but also by three additional factors: osmotic pressure, hydrogen ion concentration (pH level), and spring temperature.
Osmotic Pressure
(Hypotonic, Weakly alkaline, High temperature spring)
In hot spring classification, “osmotic pressure” refers to comparing the concentration of dissolved components in the spring water (mainly salts) with that of human body fluids (such as blood and intracellular fluid). Based on this comparison, springs are categorized as hypotonic, isotonic, or hypertonic. The difference in concentration serves as an indicator of how easily water moves between the hot spring water and body fluids.
Total Dissolved Substances
1,180 mg/kg
Classified as a Hypotonic spring
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Isotonic It has the same osmotic pressure as human body fluids. This is equivalent to a saline solution made by dissolving 8.8 g of salt in 1 liter of water. Because its concentration is close to that of body fluids, there is minimal movement of water and minerals due to osmotic pressure, making it the least stimulating and placing the least burden on the body. |
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Hypertonic Water is more likely to be drawn out of the body, while hot spring minerals are more readily absorbed, allowing for stronger therapeutic effects. However, it can also cause “yu-atari” (bath fatigue) more easily and may be more physically demanding. It is generally considered a “strong” or highly concentrated hot spring. |
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Hydrogen Ion Concentration
(Hypotonic, Neutral, High temperature spring)
In the hot spring analysis report, the section titled “Examination and test results at gushing location” includes the listed pH value. Chemically, a pH of 7.0 is considered neutral; values below this are acidic, and values above it are alkaline. According to the “Guidelines for the Mineral Spring Analysis Methods”, the chemical nature of a mineral spring is classified based on its pH value at the time of emergence, as shown in the table below.
pH 6.4
Classified as Neutral
Spring Temperature
(Hypotonic, Neutral, High temperature spring)
60.5℃
Classified as High temperature spring
Under the “Hot Springs Act”, water that contains one or more designated substances at or above the legally specified levels and has a source temperature of 25°C or higher is classified as a “hot spring”. If the temperature is below 25°C, it is labeled a “cold mineral spring”. Furthermore, as noted above, hot springs are classified by source temperature as high-temperature spring, hot spring, or low-temperature spring.
Standing Bath in the Large Public Baths for men and women “Mori-no-Yu”
When the bathhouse was renovated in 2009, the “Deepest Standing Bath in Japan” was created in the men's bath. There is a wooden stick to hold on to, but please be careful when bathing. In winter, when the leaves are falling, the view of the satoyama can be seen through the branches of the trees.
Facility Data
| Founded in | 2002 (Heisei 14) |
|---|---|
| Check in | 3:00 PM |
| Check out | 10:00 AM |
| Location | Mountains |
| Rooms | Total of 9 rooms (6 Japanese-style rooms [all with bath and toilet], and 3 Japanese-Western style rooms [all with bath and toilet]) |
| Capacity | 45 persons |
| Parking | 20 cars |
| Facilities | Shop, Foot bath |
| Internet | Wi-Fi available |
| Barrier-free | Not supported |
| Bidet toilet | Equipped |
Keywords for this inn
| Located on a hillside at the edge of Kurokawa Onsen, offering sweeping views over the valley |
| All rooms feature private open-air baths with natural free flowing hot spring water |
| Every room is a detached villa, providing a secluded stay surrounded by nature |
| A scenic private open-air bath available exclusively for guests |
| Creative kaiseki cuisine featuring a modern take on Kumamoto flavors |
Hot Spring (Onsen) Report
| Kurokawa Onsen has become one of the most popular hot spring areas not only in Kumamoto Prefecture and Kyushu, but also in Japan. The hot spring town stretches along the Tanoharu River in a valley, and is mainly made up of small-scale inns with 30 or fewer guest rooms. The exterior of the inns, all with clay walls and kawara tiled roofs, combined with the surrounding countryside,... Read more → |
Transportation Access
| By bus | ○From Fukuoka: Express buses are available via Hakata Station, Tenjin Station, and Fukuoka Airport (Nishitetsu Express Bus)
○From Kumamoto: Highway buses available via Kumamoto Station, Aso Kumamoto Airport, and Aso Station (Trans Kyushu Bus) ※For Trans Kyushu Bus, there are two types of buses: one includes sightseeing in Aso and the other does not. Also available from Beppu area. ※Sanko Bus is also available from Kumamoto area. Nishitetsu Express Buses are available for Hita Station (many services, transfer at Hita Station) and for Tsuetate Onsen (few services). |
|---|---|
| Shuttle bus | None |
| By car | From Oita Expressway “Hita IC”, 60 min. on Route 212, 70 min. from “Yufuin IC”. 90 min. from Kyushu Expressway “Kumamoto IC”. |
| Address | Kumamoto / Kurokawa Onsen / Ryokan Kounoyu
6784 Manganji, Minami-Oguni machi, Aso-gun, Kumamoto 869-2402 TEL:+81-(0)967-48-8700 |