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, Weakly alkaline, High temperature spring)
Deeply hydrating, lasting warmth from free-flowing hot 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
432 mg/kg
87.72 mval%
■ Moisturizes and helps soothe dry skin
■ Relieves muscle tension and eases pain
■ Promotes blood circulation, helping to reduce sensitivity to cold
■ Stimulates metabolism and supports natural detoxification
645 mg/kg
84.64 mval%
■ Effective for minor cuts due to the bactericidal effect of salt
■ Salt coats the skin, helping lock in warmth
■ Sustained warmth helps balance the autonomic nervous system
■ Salt coating helps lock in moisture
*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 200 mg/kg
■ Dewy and moisturizing effect
■ 4 times the hot spring standard value (50 mg/kg)
Metaboric Acid 35.3 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)
1,554 mg/kg
About 10-15 times more components compared to commercial bath additives!
Hydrogen Ion
Concentration
pH 7.9
Weakly alkaline
Spring Temperature
80.3 ℃
■ The flow rate is adjusted to maintain the ideal temperature
Color of water /
Smell of water
Clear and Colorless
Odorless
Volume of water
100 L/min
（Piped hot spring water/
Mechanically pumped)
Hot Spring Water Flow per Person (Spring Discharge Rate / Maximum Guest Capacity)
→ 100 L÷30 guests ＝3.3 L/min per guest
*Note: For 100% free-flowing hot spring water (gensen kakenagashi), a minimum flow rate of 1 L/min per bather is generally regarded as a guideline.
Status of Hot Spring Utilization
| Water added | Heated | Disinfected | Circulated | Bath additives |
|---|---|---|---|---|
| Yes／Ｎo | 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 on‑site spring water or well water)
Large Puplic Open-air bath (for women)
Beyond the indoor large public bath lies a spacious open-air bath with a wonderfully open atmosphere, where guests can enjoy a rustic hot spring bathing experience surrounded by nature. The water here is a blend of the main “Sodium - Chloride springs” (Weakly alkaline spring with a pH of 7.9) and a Simple Hot Springs (Neutral, with a pH of 7.0).
Skin Feeling Gauge
Ideal for:
People interested in skin-beautifying effects
People with dry skin
People with minor cuts
People looking to relax and relieve stress
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”
Outside the main building area where the guest rooms are located, through the parking area, and across a small road is a bathhouse. Two private open-air baths are located in it. Its peaceful and tranquil atmosphere is part of its charm, while the songs of small birds provide a soothing accompaniment.
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 weakly alkaline 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).
Family Bath “Momiji”
This private bath was newly opened in October 2017 and is referred to by the inn as a “Family bath”. The cypress bathtub provides a wonderfully soothing bathing experience. Another private bath, “Tsukushi”, features a stone-built tub. Although every guest room at the inn is equipped with its own private open-air bath, these baths are perfect for guests who would like to enjoy a slightly different atmosphere.
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
1,554 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, Weakly alkaline, 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 7.9
Classified as Weakly alkaline,
Spring Temperature
(Hypotonic, Weakly alkaline, High temperature spring)
80.3℃
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 bathe together comfortably, allowing guests to enjoy a deeply relaxing soak. A roof is also built over the bath, so it can be enjoyed even on rainy days. In addition to this “Akaishi-buro bath”, other guest rooms feature distinctive bath styles such as the “Kiriishi-buro bath”, “Kuroishi-buro bath”, and “Hinoki-buro bath” each with its own unique character.
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 80.3°C) drawn from Sujiyu Onsen Supply Corporation. The hydrogen ion concentration is pH 7.9 (Weakly alkaline). Weakly alkaline hot springs help... 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 |