Fukushima Prefecture is renowned as one of Japan's premier hot spring destinations, particularly celebrated for its abundance of hidden hot springs. Nestled in mountainous areas within Bandai-Asahi National Park and Nikko National Park, the region offers diverse hot springs ranging from wild natural baths to historic single-inn retreats. This article introduces ten carefully selected secret hot springs in Fukushima Prefecture.
1. Numajiri Onsen Motoyu (Inawashiro Town)
Numajiri Motoyu, located at approximately 1,250 meters altitude on the slopes of Mount Adatara, is a wild onsen boasting Japan's largest single-source spring output. Its discharge reaches 13,400 liters per minute, with a history spanning over 270 years since its opening in 1751 (Horeki era) during the Edo period.
The most spectacular feature is the river itself becoming hot spring water - a breathtaking sight. Natural bathing pools are scattered throughout, truly deserving the title "wild onsen paradise." The spring quality is acidic calcium/aluminum sulfate/chloride spring with pH 1.7-2.1, as acidic as lemon. Abundant yunohana (mineral deposits) are harvested and distributed to other hot spring areas.
Once off-limits due to toxic hydrogen sulfide gas, since 2020 local hot spring associations have organized safety-managed "Extreme Onsen Experience Tours," making visits possible through guided tours.
- Spring Quality: Acidic calcium/aluminum sulfate/chloride spring
- Source water flow-through
- Bathing Facilities: Wild onsen (multiple natural pools)
- Source Temperature: Approximately 80°C
- pH: 1.7-2.1
- Day-use Bathing: Available (guided tour participation required)
- Accommodation: Not available (wild onsen. Nearby Numajiri Onsen lodgings available)
- Operating Period: Early June - early November (Extreme Onsen Tour season)
- Tour Fee: Varies by group size (inquiry required)
- Contact: cafe&activity nowhere (TEL: 0242-93-7081)
2. Tokusa Onsen Iwaburo (Minamiaizu Town)
Tokusa Onsen, located in the Nishine River valley of Minamiaizu Town, is a hidden hot spring said to have been discovered approximately 1,000 years ago. Its name derives from the horsetail plants that once grew abundantly in the area.
The main attraction is the outdoor rock bath that springs from the riverbed. The bath carved from rock has hot spring water at approximately 45 degrees Celsius bubbling up from beneath, allowing bathers to soak in 100% pure spring water without it touching air. Among hot spring enthusiasts, it is considered "a must-visit hidden hot spring at least once in a lifetime." Visitors can heal their mind and body while listening to the murmur of the clear stream and enjoying nature throughout the four seasons.
Although the rock bath has been destroyed multiple times by typhoon damage, it has been rebuilt each time with donations from hot spring fans across Japan, demonstrating how beloved this hot spring is.
- Spring Quality: Simple sulfur spring
- Source water flow-through
- Bathing Facilities: Rock bath (wild onsen)
- Source Temperature: 45°C
- Operating Hours: 24 hours
- Day-use Bathing: Available (free)
- Accommodation: Available at nearby ryokan and minshuku (such as Tokusa Onsen Izutsuya)
- Operating Period: April 1 - December 31 (closed in winter)
3. Futamata Onsen Daimaru Asunaroso (Tenei Village)
Futamata Onsen, located at 800 meters altitude in Tenei Village, Iwase District, Fukushima Prefecture, is a historic hot spring that opened in the Heian period in 969 CE. It is also known as the birthplace of the term "hidden hot spring," and the owner of Daimaru Asunaroso serves as honorary chairman of the Association to Preserve Japan's Secret Hot Springs.
The main attraction is the self-spouting pothole bath. This unique bathing facility has spring water bubbling directly from rock formations that were once a riverbed. Guests can use it in alternating male and female time slots. There are also separate outdoor baths for men and women along the Futamata River, where visitors can enjoy supreme source water bathing in a wild atmosphere surrounded by primeval beech forests.
Dinner features local cuisine centered on mountain vegetables and river fish, allowing guests to enjoy a back-to-nature journey.
- Spring Quality: Simple spring
- Source water flow-through
- Bathing Facilities: Indoor baths=2, outdoor baths=3, self-spouting rock bath=1
- Source Temperature: 58°C
- No dilution or heating
- Day-use Bathing: Available (adults 800 yen) 11:00-14:30
- Accommodation: Available
- Operating Period: Late April - mid-November (closed in winter)
7. Washikura Onsen Kogen Ryokan (Fukushima City)
Washikura Onsen, located at the high altitude of 1,230 meters, is considered one of the coolest places in Fukushima Prefecture, with temperatures about 10 degrees lower than Fukushima City even in summer. It is a member inn of the Association to Preserve Japan's Secret Hot Springs.
The main feature is having two different spring qualities: acidic green vitriol spring and weak sulfur spring. The acidic green vitriol spring is pale reddish-brown and is also called "medicinal hot spring," long cherished as a famous cure for digestive and neurological ailments. A drinking spring fountain is also provided. The weak sulfur spring is milky white with abundant yunohana (mineral deposits) and has gentle softness on the skin.
On some mornings, a sea of clouds can be seen, delighting bathers. The ryokan offers excellent hot springs, meals, clean facilities, and attentive staff - a well-balanced hidden hot spring inn.
- Spring Quality: Acidic green vitriol spring, weak sulfur spring
- Source water flow-through
- Bathing Facilities: Indoor baths=2, outdoor baths=2
- Source Temperature: 50°C, 71°C
- No dilution or heating
- Day-use Bathing: Available (adults 800 yen)
- Accommodation: Available
- Operating Period: Mid-April - late November (closed in winter)
8. Kashiwa Onsen Ryokan Daikokuya (Nishigo Village)
Kashiwa Onsen, nestled at approximately 900 meters altitude along the Abukuma River headwaters within Nikko National Park, is a single remote inn beloved by Matsudaira Sadanobu, the feudal lord of Shirakawa Domain. A member of the Association to Preserve Japan's Secret Hot Springs, it features a main building constructed in 2009 and a wooden annex once favored by Lord Matsudaira.
The signature feature is the "Great Rock Bath" - a unique standing bathing pool carved from natural rock formations, measuring 15 meters long, 5 meters wide, and approximately 1-1.2 meters deep. In this secluded location surrounded by clear streams nurtured by primeval beech forests, visitors can slowly soak in pure spring water.
All bathing facilities maintain commitment to source water flow-through with no dilution, heating, or circulation.
- Spring Quality: Simple spring
- Source water flow-through
- Bathing Facilities: Indoor baths=2, outdoor baths=2, great rock bath=1
- Source Temperature: 60°C
- No dilution, heating, or circulation
- Day-use Bathing: Available (adults 700 yen) 10:00-15:00
- Accommodation: Available
- Operating Period: Year-round
9. Nakanosawa Onsen Onyado Manyotei (Inawashiro Town)
Nakanosawa Onsen, located on the western slope of Mount Adatara at 1,000 meters altitude on a highland plateau, was established approximately 380 years ago during the Bunroku era. The source is the same "Numajiri Motoyu" from near the crater of Mount Adatara as Numajiri Onsen, boasting Japan's largest single-source output of 13,400 liters per minute.
Onyado Manyotei began operations in 1991 as an annex of the 130-year-old Ogawaya Ryokan, exclusively for guests aged 16 and above. Away from the hot spring town, with primeval forests spreading before it, the only sounds are bird songs and stream murmurs - a space of tranquility.
The spring quality is acidic sulfur spring with pH 1.7-2.1, as acidic as lemon, but the skin feel is like silk as the water is tempered through long pipes. The all-wooden large bath is filled with the scent of hinoki cypress, and the adjacent outdoor bath offers unobstructed views.
- Spring Quality: Acidic spring (sulfur spring)
- Source water flow-through
- Bathing Facilities: Indoor baths=2, outdoor baths=2, private semi-outdoor bath=1
- Source Temperature: Approximately 50°C
- No dilution or heating
- Day-use Bathing: Not available
- Accommodation: Available (ages 16 and above only)
- Operating Period: Year-round
10. Oze Hinoemata Onsen Hiuchi no Yu (Hinoemata Village)
Located at the southernmost point of Fukushima Prefecture, Hinoemata Village is called "Japan's last unexplored region" - a quiet mountain village. As the gateway to Oze, Hiuchi no Yu is the only public bathhouse among three that offers source water flow-through day bathing.
Built on a hill overlooking the Funaki River, it luxuriously uses its own simple sulfur spring source in flow-through style. Both indoor and outdoor bathing facilities are equipped, allowing visitors to relax while viewing the four-season expressions of Hinoemata Village.
The facility, built in 1999, is meticulously maintained with an atmosphere like a luxury resort hotel. It is beloved by many mountaineers as a post-climb stop after hiking Oze or Mount Aizu-Komagatake.
- Spring Quality: Simple sulfur spring
- Source water flow-through
- Bathing Facilities: Indoor baths=2, outdoor baths=2
- Source Temperature: 62.4°C
- pH: 9.1
- No dilution or heating, no chlorine disinfection (except during cleaning)
- Day-use Bathing: Available (adults 500 yen) 6:00-21:00
- Accommodation: Available at nearby ryokan and minshuku (such as Ryokan Hinoemata)
- Operating Period: Year-round (Tuesday morning cleaning)
Conclusion
Fukushima Prefecture's hidden hot springs offer diverse attractions, from wild onsen to single remote inns. All are committed to source water flow-through with no dilution or heating, providing hot spring experiences in harmony with nature.
Why not embark on a journey to heal mind and body at a mountain hidden hot spring surrounded by primeval beech forests, away from daily hustle and bustle?
Notes
- While the information represents the latest available at the time of research, there may be errors. Please verify the most current information on official websites.
- Many facilities close during winter, so please confirm operating status before visiting.
- Day-use bathing hours and fees are subject to change.
- Wild onsen (rock baths, Numajiri Motoyu) may be unavailable depending on weather and water levels. Numajiri Motoyu in particular is a dangerous location with toxic hydrogen sulfide gas, and guided tour participation is mandatory. Individual visits are extremely dangerous. Period: Year-round
4. Takayu Onsen Adachiya (Fukushima City)
Takayu Onsen, quietly nestled in the mountains at 750 meters altitude, boasts over 400 years of history and is counted among the "Three Great Hot Springs of Oshu" along with Yamagata's Zao Onsen and Shirabu Onsen. Known for its rare high-concentration sulfur springs, it has repeatedly won first place in Jalan's Hot Spring Destination Satisfaction Rankings.
Adachiya is the oldest established ryokan in Takayu Onsen, having completed renovation of its large bath in July 2025. The signature large outdoor bath "Taiki no Yu" is shaped like a river and features waterfall bathing, lying-down bathing, and cave bathing. Two lounges were also newly established in 2024, where guests can enjoy beverages throughout their stay.
Dinner is a course meal enjoyed while grilling seafood and mountain delicacies over an irori hearth. The head chef holds qualifications as both sommelier and sake taster, with deep commitment to food and drink pairings.
- Spring Quality: Sulfur-containing calcium/aluminum sulfate spring (hydrogen sulfide type)
- Source water flow-through
- Bathing Facilities: Indoor baths=2, large outdoor baths=2 (alternating for men/women), private outdoor baths=2, private indoor bath=1
- Source Temperature: 46.3°C
- pH: 2.7
- No dilution or heating
- Day-use Bathing: Suspended until around April 2025 due to construction
- Accommodation: Available (junior high school age and above only)
- Operating Period: Year-round
5. Takayu Onsen Tamagoyu (Fukushima City)
Also a hidden hot spring in Takayu Onsen, Tamagoyu is an established ryokan founded in 1868. It was named because bathing makes skin as smooth as an egg, and the smell resembles boiled eggs.
The garden contains a thatched-roof bathhouse that preserves the atmosphere from the founding era, evoking 150 years of history. Visitors can enjoy white cloudy spring water that has been naturally flowing for 400 years at seven different bathing facilities. The ryokan is committed to 100% source water flow-through with no dilution or heating.
During the post-war high economic growth period, Takayu Onsen imposed a self-restriction of "no entertainment," going against the times to preserve the traditional atmosphere of a hot spring cure resort. This attitude has led to today's blessings.
- Spring Quality: Acidic sulfur-containing aluminum/calcium sulfate spring (hydrogen sulfide type)
- Source water flow-through
- Bathing Facilities: Indoor baths=2, outdoor baths=5
- Source Temperature: 44°C
- pH: 2.8
- No dilution or heating
- Day-use Bathing: Available (adults 1,000 yen) 10:00-15:00
- Accommodation: Available
- Operating Period: Year-round
6. Makukawa Onsen Mitoya Ryokan (Fukushima City)
Makukawa Onsen, located in Bandai-Asahi National Park at approximately 1,300 meters altitude on the slopes of Mount Azuma, is a hidden hot spring founded in 1891. It is also a member of the Association to Preserve Japan's Secret Hot Springs.
The ryokan has two source springs - the indoor bath uses "simple spring" while the outdoor bath "Saeri no Yu" located in a separate area uses "simple sulfur spring," allowing visitors to enjoy two different spring qualities at once. The particularly popular "Saeri no Yu" along the mountain stream features beautiful bluish milky-white source water flowing through.
Surrounded by primeval beech forests and a treasure trove of untouched nature, the area features a pond connected directly to natural mountain streams stocked with yamame trout, iwana char, and carp. Mornings begin with the scent of sulfur.
- Spring Quality: Simple spring, simple sulfur spring
- Source water flow-through
- Bathing Facilities: Indoor baths=2, outdoor baths=2
- Source Temperature: 44.9°C, 72.5°C
- No dilution or heating
- Day-use Bathing: Available (adults 600 yen)
- Accommodation: Available
- Operating