Kyushu > Ooita > Sujiyu Onsen
A secluded hot spring retreat with private open-air baths in every room, set amidst the pristine nature of Kokonoe.
Yamaai-no-Yado KIYASUYA
山あいの宿 喜安屋
527 Sujiyu Onsen, Kokonoe-machi, Kusu-gun, Oita 879-4912, JAPAN
Phone：+81-(0)973-79-3341
Spring Quality
Sodium － Chloride springs
ナトリウム－塩化物泉
(Hypotonic, Neutral, High temperature spring)
Deeply hydrating, lasting warmth from free-flowing springs／
Private open-air baths in every room at this secluded mountain inn
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
426 mg/kg
89.78 mval%
■Helps improve dry skin with its moisturizing properties
■Relieves muscle tension and eases pain
■Promotes blood circulation, helping to reduce sensitivity to cold
■Stimulates metabolism and supports the body’s natural detoxification process
613 mg/kg
87.32 mval%
■Effective for minor cuts due to the bactericidal effect of salt
■Salt helps seal the sweat glands, enhancing the heat-retention effect
■Salt coating supports better moisture retention
■The sustained warmth contributes to balancing the autonomic nervous system
*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 157 mg/kg
■Dewy and moisturizing effect
■More than 3 times the hot spring standard value (50 mg/kg)
Metaboric Acid 37.1 mg/kg
■Cleansing effects that help keep the skin clean
■About 7 times the hot spring standard value (5 mg/kg)
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Total Dissolved Substances
(excluding gaseous)
1,421 mg/kg
About 9-14 times more components compared to commercial bath additives!
Hydrogen Ion
Concentration
pH 7.1
Neutral
that is kind to the skin!
Spring Temperature
76.9 ℃
■ Large public baths, Open-air baths, and In-room Open-air baths･･･
Water flow is adjustable to maintain the ideal temperature
Color of water /
Smell of water
Clear and Colorless
Odorless
Volume of water
100 liters per minute
(Piped / Mechanically pumped)
Hot spring water usage per person (spring discharge / maximum capacity)
→ 100 liters / 30 guests ＝3.3 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 |
|---|---|---|---|---|
| Yes／No | Yes／No | No | No | No |
*All baths are supplied with 100% natural free-flowing hot spring water
*Water may be added during the hot summer months (using untested natural spring
Large Puplic Open-air bath (for women)
Day visitors can also use the gender-separated large public baths and open-air baths. This bath is a mixture of the main “Sodium - Chloride springs” and high-temperature “Weak Alkaline Simple Springs” to adjust the temperature.
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
Indications by Spring Quality
(for bathing)
Cuts
Autonomic instability
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
Private Open-air Bath “Fuku-no-Yu”
Just outside the main building where the guest rooms are located, across the parking area and a small road, stands a bathhouse. Inside are two private open-air baths. The tranquil setting is part of its charm. Exclusive to overnight guests.
Keywords of this Onsen
The salt’s bactericidal properties help treat minor cuts
A salt coating provides a long-lasting, deeply warming effect, helping prevent chills and relieve sensitivity to cold. It improves peripheral circulation and helps regulate the autonomic nervous system, making it beneficial for depressive states and supporting mental health
① The salt’s moisturizing effect on the skin (chloride spring and metasilicic acid content of 100 mg/kg or more) and ③ the salt’s coating action of its active components (chloride spring — known as a “Hot springs for the finishing touch”) help relieve dry skin conditions. ② Its neutral nature is gentle on sensitive skin, leaving it smooth after bathing. ④ It also has a cleansing effect that helps prevent acne (metaboric acid content of 10 mg/kg or more).
Its neutral nature is gentle on sensitive skin
Family Bath “Momiji”
An indoor private family bath featuring a soothing hinoki (Japanese cypress) tub. There is also a stone bath named “Tsukushi”, while the hinoki bath is called “Momiji”. Exclusive to overnight guests.
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, Neutral, 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
1,421 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 7.1
Classified as Neutral
Spring Temperature
(Hypotonic, Neutral, High temperature spring)
76.9℃
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.
Guest room open-air bath of the 10-tatami “Kaze” type (“Akaishi-buro”, a red stone bath)
The bathtub is spacious enough for two adults to enjoy a relaxing soak together. A roof covers the tub, so you can bathe comfortably even in the rain. Exclusive to overnight guests.
Facility Data
| Founded in | 1967 (Showa 42) / Relocated in 2006 (Heisei 18) |
|---|---|
| Check in | 3:00 PM |
| Check out | 10:00 AM |
| Location | Mountains |
| Rooms | Total 10 rooms 10 Japanese-style rooms (all with open-air baths and toilets) |
| Capacity | 30 persons |
| Parking | 10 cars |
| Facilities | － |
| Internet | Wi-Fi access in all areas |
| Barrier-free | － |
| Bidet toilet | Equipped |
Keywords for this inn
| All 10 guest rooms are detached and feature private open-air baths |
| Facility buildings are connected by covered outdoor walkways |
| Wild, nature-inspired private open-air baths with free-flowing hot spring water |
| A tranquil mountain retreat rich in the atmosphere of a secluded hot spring |
| Exquisite seasonal cuisine featuring the finest local ingredients |
Hot Spring (Onsen) Report
| “Yamaai-no-Yado KIYASUYA” uses two types of spring sources. The main source is a “Sodium - Chloride springs” (temperature 76.9°C) drawn from Sujiyu Onsen Supply Co. It is a hot spring containing salt, which has a bactericidal effect, and bathing in it can reduce Cuts and... Read more → |
Transportation Access
| By train | JR Bungo Nakamura Station - 45 min. by bus - “Sujiyu Onsen” bus stop |
|---|---|
| By car | (From Oita/Fukuoka) 30 min. from Kokonoe IC on Oita Expressway (From Kumamoto) 2 hours by Yamanami Highway, etc. |
| Address | 527 Sujiyu Onsen, Kokonoe-machi, Kusu-gun, Oita 879-4912, JAPAN Phone:+81-(0)973-79-3341 |