Gunma Prefecture is known as one of Japan's premier hot spring regions, famous not only for well-known destinations like Kusatsu Onsen and Ikaho Onsen but also for numerous secluded hot springs nestled in mountain valleys. This guide introduces 10 carefully selected hidden hot springs in Gunma, ranging from wild natural baths to historic single-inn retreats, each with its own unique charm and objective information.
1. Hoshi Onsen Chojukan (Minakami Town)
Located within Joshinetsu Kogen National Park near the border between Gunma and Niigata prefectures, Hoshi Onsen Chojukan is a historic inn established in 1875. The main building, designated as a National Registered Tangible Cultural Property, evokes the atmosphere of an Edo-period inn with its distinctive black-walled wooden architecture and bark-shingled roof.
The inn's signature bath, "Hoshi-no-yu," was built in 1895 in the Rokumeikan style. Its four bathtubs are filled with spring water bubbling up from directly beneath the floor. The crystal-clear water is so transparent that the pebbles on the bottom are clearly visible, offering an authentic "ashimoto funshutsu" (foot-level spring emergence) experience. Many literary figures, including Yosano Akiko and Kawabata Yasunari, visited this location and left their works.
Guest rooms include the main building, an annex along the Hoshi River, the spacious Kunzan-so, and Horyuden built in 1989, each offering spaces filled with tradition and dignity. Dinner features local ingredients such as Joshu beef and Joshu pork, and guests can enjoy the inn's original sake.
- Spring Quality: Calcium/Sodium-Sulfate Spring
- Free-flowing spring water
- Baths: Multiple indoor and outdoor baths
- Source Temperature: Approximately 43°C
- Water Addition/Heating: None
- Day-use Bathing: Available (confirmation required)
- Overnight Stay: Available
- Operating Period: Year-round
2. Shiriyaki Onsen (Kawa-no-yu) (Nakanojo Town)
The "Kawa-no-yu" at Shiriyaki Onsen is a wild hot spring representative of the Kanto region, where hot spring water emerges from the riverbed of the Nagasazawa River. The massive open-air bath created by damming the river is truly a natural hot spring pool created by nature itself.
The name originates from the practice of sitting on stones warmed by the hot spring water emerging from the riverbed to treat hemorrhoids - literally "burning the bottom." The vast open-air bath, approximately 30 meters square, presents the amazing sight of a river that is itself a hot spring.
Hot springs emerge from various points on the riverbed, with temperatures varying by location. Swimsuit use is recommended, and bathing is available 24 hours a day free of charge. However, bathing may not be possible during heavy rain or snowmelt when the river's water volume increases, so caution is advised when visiting. Nearby accommodation facilities allow visitors to fully enjoy the wild hot spring experience.
- Spring Quality: Calcium/Sodium-Sulfate/Chloride Spring
- Free-flowing spring water
- Baths: Open-air bath (the river itself)
- Source Temperature: Varies by location
- Water Addition/Heating: None (natural state)
- Day-use Bathing: Available (24 hours, free)
- Overnight Stay: Use nearby accommodations
- Operating Period: Year-round (weather dependent)
3. Takaragawa Onsen Osenkaku (Minakami Town)
Takaragawa Onsen Osenkaku, established in 1923, is a single inn nestled in the mountains of the Tanigawa mountain range, with its greatest attraction being the large-scale open-air baths scattered along the clear stream of the Takaragawa River.
Beginning with "Maka-no-yu," which occupies approximately 120 tatami mats and was created in 1940, four large open-air baths have been constructed, with a combined area totaling 470 tatami mats. The milky-white water, luxuriously free-flowing at 1,800 liters per minute, carries the scent of sulfur, allowing guests to enjoy hot springs in the midst of magnificent nature.
Three mixed-gender large open-air baths that can be enjoyed while wearing bathing attire, plus a women-only open-air bath, offer exceptional bathing experiences surrounded by nature's changing seasonal expressions. Dinner features colorful arrays of seasonal mountain vegetables and river fish, showcasing the flavors unique to mountain villages.
- Spring Quality: Simple Spring
- Free-flowing spring water
- Baths: Multiple indoor baths, 4 outdoor baths (total 470 tatami mats)
- Source Temperature: Approximately 46°C
- Water Addition/Heating: None
- Day-use Bathing: Available (Adults 1,000 yen)
- Overnight Stay: Available
- Operating Period: Year-round
4. Shima Onsen Sekizenkan (Nakanojo Town)
Sekizenkan, established in 1694, is a hot spring inn with over 300 years of history. The main building, built in 1694, is said to be Japan's oldest wooden hot spring inn architecture and is designated as an Important Cultural Property of Gunma Prefecture.
"Genroku-no-yu," built in 1925, is designated as a National Registered Tangible Cultural Property and Gunma Prefecture Modern Heritage site, featuring a charming retro-modern atmosphere reminiscent of the Taisho era. Large arched windows allow light to stream into the space where guests can enjoy bathing. It is said to be one of the model inns for Hayao Miyazaki's animated film "Spirited Away," with the scenery featuring a red bridge attracting many fans.
Sekizenkan consists of three buildings: the main building (hot spring treatment facility), Sanso, and Kashoutei, each with its own distinct character. The main building offers traditional hot spring treatment experiences with self-service as the basic principle. Dinner features simple yet rich-flavored cuisine using seasonal vegetables and mountain vegetables from the Shima Onsen area, Gunma Prefecture's famous konnyaku, tofu, and other ingredients.
- Spring Quality: Sodium/Calcium-Chloride/Sulfate Spring
- Free-flowing spring water
- Baths: Multiple indoor baths, private baths available
- Source Temperature: Approximately 56°C
- Water Addition/Heating: Varies by facility
- Day-use Bathing: Available (main building confirmation required)
- Overnight Stay: Available
- Operating Period: Year-round
5. Yashio Onsen Shinsuikan (Fujioka City)
Shinsuikan, established in 1931, is a member inn of the Japan Secret Hot Spring Association nestled along the Kanna River. The interior, filled with a Taisho-era romantic atmosphere, and the Japanese garden outside the windows that changes colors with the seasons are its main attractions.
The greatest characteristic of Yashio Onsen is its hot spring called "ancient seawater," said to be seawater from the Tertiary Period of the Cenozoic Era (65 million to 2 million years ago) trapped underground and now emerging. Because the source temperature is low at 15°C, the large bath has both a heated bath with added water and heating, and a cold bath at natural emerging temperature, allowing guests to enjoy alternating hot and cold bathing.
This unusual cold mineral spring allows visitors to experience a beach-like atmosphere in landlocked Gunma Prefecture, characterized by very high salt concentration. Bathing in the cold spring during summer is exceptional, and the convenient access of approximately 1.5 hours by car from central Tokyo is also attractive. Cuisine includes rice and yudofu cooked using Yashio Onsen water, as well as various local dishes.
- Spring Quality: Sodium-Chloride/Bicarbonate Cold Mineral Spring
- Free-flowing spring water
- Baths: Indoor baths (one each for men and women), Outdoor bath (mixed)
- Source Temperature: 15°C
- Water Addition/Heating: Heating only for hot bath
- Day-use Bathing: Not available (overnight guests only)
- Overnight Stay: Available
- Operating Period: Year-round
6. Manza Onsen Nisshinkan (Tsumagoi Village)
Manza Onsen Nisshinkan, located at an altitude of 1,800 meters, is known as the hot spring inn closest to the stars. Spring water naturally flows from within the premises, boasting an overwhelming volume of 1,800 liters per minute and 5.4 million liters per day.
The spring quality is acidic sulfur spring with one of Japan's highest sulfur concentrations, characterized by milky white turbid water. The hot spring possesses all five ideal qualities: natural flow, white turbidity, high temperature, therapeutic effects, and free-flowing. There are three bathing facilities emphasizing natural wood construction, with the panoramic open-air bath "Gokuraku-no-yu" being particularly popular for its spectacular views of the Manza mountains and starry sky.
The large bath "Choju-no-yu" offers six types of bathtubs including 100% pure spring water "Uba-yu," "Niga-yu" for large groups, and "Taki-yu" with waterfall massage. Meals are buffet-style for both breakfast and dinner, featuring balanced menus of over 40 Japanese, Western, and Chinese dishes emphasizing "ma-go-wa-ya-sa-shi-i" (balanced nutrition).
- Spring Quality: Acidic Sulfur Spring
- Free-flowing spring water
- Baths: Multiple indoor and outdoor baths (9 hot springs total)
- Source Temperature: Approximately 80°C
- Water Addition/Heating: None
- Day-use Bathing: Available (Adults 1,000 yen, 10:00-17:00)
- Overnight Stay: Available
- Operating Period: Year-round
7. Kirizumi Onsen Kintokan (Annaka City)
Kintokan, established in 1884, is a secluded single inn located at approximately 1,200 meters altitude within Joshinetsu Kogen National Park. Located near the border between Gunma Prefecture and Nagano Prefecture (Karuizawa), it once prospered as a summer resort but suffered catastrophic damage from landslides in the late Meiji period, with only Kintokan continuing operations.
It is also known as the setting for Morimura Seiichi's mystery novel "The Proof of the Man," with items from that era displayed inside the inn. Many politicians and cultural figures, including Ito Hirobumi and the Yosano Tekkan-Akiko couple, visited this historic hot spring.
The hot spring has a source temperature of approximately 40°C and is lukewarm, with free-flowing spring water without water addition or heating. It has a reputation as a high-quality hot spring with a sulfur scent. While the inconvenient location requires a 20-minute walk from the parking lot to the inn (or 5 minutes by shuttle microbus), this allows visitors to experience the atmosphere of a secluded mountain hot spring surrounded by silence. Cuisine features simple mountain village dishes using locally harvested wild vegetables.
- Spring Quality: Calcium-Sulfate Spring
- Free-flowing spring water
- Baths: Indoor baths (one each for men and women)
- Source Temperature: Approximately 39°C
- Water Addition/Heating: None
- Day-use Bathing: Available (700 yen, 10:00 to before sunset)
- Overnight Stay: Available
- Operating Period: Year-round
8. Hanashiki Onsen Irori-no-Oyado Hanashiki-no-yu (Nakanojo Town)
Hanashiki Onsen is a historic hot spring said to have been discovered in 1192 when Minamoto no Yoritomo visited the area for boar hunting. It was named because cherry blossom petals floated on the water as if spread across the surface. Poet Wakayama Bokusui also visited this location and left tanka poetry.
Currently, "Irori-no-Oyado Hanashiki-no-yu" operates as the only hot spring inn, a secluded single inn limited to 4 rooms. Though located only 800 meters from Shiriyaki Onsen, the spring quality differs. The convenient access of approximately 25 minutes by car from Kusatsu Onsen is also attractive.
The main feature is the irori (sunken hearth) mountain kaiseki cuisine enjoyed in the irori hall featuring a large tree said to be 1,000 years old. Simple yet heartfelt cuisine using seasonal mountain delicacies and stream fish is provided. The hot spring is free-flowing, with outdoor baths, indoor baths, and private baths available.
- Spring Quality: Calcium/Sodium-Sulfate/Chloride Spring
- Free-flowing spring water
- Baths: Indoor baths (one each for men and women), Outdoor bath (1), Private outdoor bath (1)
- Source Temperature: Approximately 50°C
- Water Addition/Heating: Heating available (winter)
- Day-use Bathing: Not available
- Overnight Stay: Available
- Operating Period: Year-round
9. Garameki Onsen (Wild Hot Spring) (Shinto Village)
A wild hot spring located at approximately 1,300 meters altitude in the Haruna Mountains, where hot spring inns once stood. Developed by local residents in 1898, it prospered as a summer resort from the Meiji to Taisho periods, but after WWII, the land was requisitioned for Self-Defense Force base construction and buildings were demolished.
After being neglected for many years, volunteers restored the spring buried in sediment to allow bathing. Currently, a drainage pipe is buried vertically in the ground, with the interior serving as the bathtub in a unique structure.
The hot spring mixes with river water, with a perceived temperature of approximately 30°C. Visiting during summer is recommended. Access involves approximately 1 hour on foot from the trailhead on Prefectural Route 28. While walking a forest road, there are sections where landslides have collapsed the road and river crossings are necessary, making it a wild hot spring suitable for those somewhat experienced in mountain walking. Stone walls, monuments, and shrines remain at the former inn site, creating a nostalgic atmosphere.
- Spring Quality: Sodium-Chloride Spring (estimated)
- Free-flowing spring water (natural emergence)
- Baths: Wild hot spring (drainage pipe)
- Source Temperature: Approximately 30°C (mixed with river water)
- Water Addition/Heating: None
- Day-use Bathing: Available (free, 24 hours)
- Overnight Stay: Not available
- Operating Period: Year-round (weather and road conditions permitting)
10. Kazawa Onsen Koyokan (Tsumagoi Village)
Kazawa Onsen, located at the high altitude of 1,500 meters, is said to have originated around 650 CE when a deer being chased by hunters healed its wounds. It prospered greatly as a hot spring treatment facility from the Edo to Taisho periods, but the hot spring town was destroyed by fire in 1918, with only Koyokan remaining at Kazawa Onsen.
Koyokan is a single inn belonging to the Japan Secret Hot Spring Association, which renovated its buildings in 2013 while preserving tradition. In a quiet environment surrounded by the nationally designated Natural Monument "Yunomaru Azalea Colony" and larch forests, the 100% natural hot spring continues to maintain free-flowing spring water without water addition or heating.
Kazawa Onsen is also known as the birthplace of "Yukiyama Sanka" (Snow Mountain Song). The hot spring is a bicarbonate spring characterized by gentle water touch and outstanding therapeutic effects. It is said to be effective for gastrointestinal disorders, sensitivity to cold, and neuralgia. Nearby hiking courses at Yunomaru Mountain and Takamine Plateau make it popular with mountaineers.
- Spring Quality: Magnesium/Sodium-Bicarbonate Spring
- Free-flowing spring water
- Baths: Indoor baths (one each for men and women), Outdoor bath available
- Source Temperature: Approximately 44°C
- Water Addition/Heating: None
- Day-use Bathing: Available (10:00-16:00, confirmation required)
- Overnight Stay: Available
- Operating Period: Year-round
Conclusion
In addition to these hidden hot springs, Gunma Prefecture has many other hot springs scattered throughout. From wild hot springs to historic long-established inns, the various hot springs each with their own unique charms provide endless exploration opportunities for hot spring enthusiasts.
When visiting hidden hot springs, it is recommended to check operating status and road conditions in advance. Particularly for wild hot springs and single inns deep in the mountains, conditions can change significantly depending on weather and season. When using wild hot springs, it is important to observe proper etiquette and care for the natural environment.
While the information presented represents the latest research at the time of compilation, errors may exist, and visitors should confirm the most current information through each facility's official website or other sources.