Hirugami Onsen is one of the most famous hot spring resorts in southern Nagano Prefecture. Located in Achi Village, Shimoina District, it is surrounded by the clear waters of the Achi River and beautiful mountain scenery.
Although the present hot spring resort has a relatively recent history, the quality of its mineral-rich water, peaceful atmosphere, and convenient location have made it a popular destination for travelers seeking a traditional Japanese hot spring experience. The area is also nationally famous for its exceptionally beautiful night skies, making Hirugami an attractive destination both day and night.
The modern history of Hirugami Onsen began in 1973, when hot spring water was unexpectedly discovered during drilling work connected with construction of tunnels for the planned Nakatsugawa Line of the Japanese National Railways.
However, historical records suggest that hot springs had been known in this area much earlier. The Shinshu Ina District Village Survey, compiled in 1740, records that people from nearby communities visited the area for hot spring treatments. An even earlier reference from 1711 mentions a place known as Yuyagongen, indicating that the area had already been associated with hot spring worship and bathing.
The earlier spring was apparently buried by a landslide and eventually disappeared from local memory. For many years, its exact location was unknown.
The hot spring was rediscovered on January 14, 1973, during boring surveys carried out for the Nakatsugawa Line construction project. Subsequent exploratory drilling confirmed a spring producing approximately 200 liters per minute at a temperature of 32.5°C.
In 1975, the Achi Development Corporation was established to promote development of the hot spring area. The following year, the village-operated health and recreation center Tsurumakiso opened, followed by the construction of numerous inns and hotels.
Today, Hirugami has developed into one of the largest hot spring resorts in southern Nagano, with more than 20 hot spring accommodations.
Hirugami Onsen is known for its alkaline simple sulfur spring. The water has a remarkably high pH of 9.7, giving it a soft and smooth quality that is often described in Japan as a “beauty bath”.
The water feels silky against the skin, and bathing in the warm spring is a particularly pleasant way to relax after exploring the surrounding mountains and valleys.
As of 2020, several source wells were in operation. The principal No. 4 and No. 5 wells are located on the right bank of the Achi River, north of the Hirugami Fault. Both provide a stable supply of highly alkaline hot spring water with a pH above 9.
The present hot spring town developed mainly from the 1970s onward. Its convenient location near the Chuo Expressway helped the resort grow rapidly, but Achi Village has also worked to preserve the peaceful character of the area.
Strict restrictions have been placed on neon signs and businesses considered inappropriate for the character of the resort. As a result, Hirugami retains a calm and relaxing atmosphere rather than the heavily commercialized appearance found in some larger hot spring destinations.
Hirugami offers a wide range of accommodations, including Hirugami Onsen Hotel Hanaya, Yumoto Hotel Achikawa, Sekitei Ishida, and Nicho-an Keigetsu.
Each property has its own character, with facilities ranging from open-air baths and garden baths to secluded bathing areas designed to evoke the atmosphere of a traditional mountain hot spring. Staying overnight allows visitors to experience the slower pace of a Japanese hot spring resort, including relaxing baths and seasonal cuisine.
You do not need to stay overnight to enjoy the hot spring water. The town has free public foot baths, including Fureai no Yu and Ahiru no Yu.
These foot baths are ideal for taking a short break while exploring the streets of Hirugami. The town also has a public heated swimming pool that uses hot spring water.
One of the most enjoyable ways to experience local life is to visit the Morning Market Square in the center of the hot spring town.
From around 6:00 a.m., local vendors offer vegetables, handmade konnyaku, pickles, and other regional products. Visitors can also encounter inago no tsukudani, grasshoppers simmered in a sweet and savory sauce, a traditional form of insect cuisine historically enjoyed in southern Nagano.
The morning market provides an opportunity to discover local foods and everyday products while experiencing a quieter side of Hirugami before the town becomes busy with visitors.
In spring, the landscape surrounding Hirugami changes dramatically. From early to late April, peach blossoms known as hanamomo bloom throughout the area, creating scenery reminiscent of a traditional Japanese paradise.
The Hanamomo Road follows National Route 256 for approximately 40 kilometers, with colorful flowering peach trees lining the route. It has become one of the most popular spring driving routes in southern Nagano.
Achi Village is internationally attractive to travelers interested in stargazing. The village has been recognized through the Ministry of the Environment’s star-observation program as a place where the stars appear exceptionally bright.
At Namiai Park, located at an elevation of approximately 1,200 meters, visitors can enjoy a spectacular night sky beneath clear mountain air. With little artificial light, countless stars become visible on clear nights, attracting stargazers from throughout Japan.
Another popular destination for stargazing is Heaven Sonohara, which provides access to the Fujimidai Highland area. A 2,500-meter-long ropeway carries visitors up to an elevation of approximately 1,400 meters.
At night, the resort holds its famous Starry Sky Night Tour, during which the lights are switched off so that visitors can experience the natural darkness of the mountain summit.
Far from the glow of city lights, the stars seem remarkably close overhead. For travelers who have never experienced Japan’s mountain night skies, this can be one of the most memorable experiences of a stay in Hirugami.
Hirugami Onsen is attractive throughout the year. Spring brings the spectacular hanamomo blossoms, while summer offers refreshing mountain greenery and the cool atmosphere of the Achi River valley.
Autumn transforms the surrounding mountains with colorful foliage, and winter brings a quiet landscape that pairs naturally with the warmth of an outdoor hot spring bath.
The combination of highly alkaline hot spring water, mountain scenery, seasonal flowers, local food, and some of Japan’s most beautiful starry skies makes Hirugami a destination that can be enjoyed in many different ways.
Hirugami Onsen is approximately 10 minutes by car from either the Iida-Yamamoto Interchange or Sonohara Interchange on the Chuo Expressway. The Sonohara Interchange is available only to vehicles traveling in the direction of Nagoya.
From Iida Station on the JR Iida Line, Shinminami Kotsu buses take approximately 30 minutes to reach the Hirugami Onsen area. There are generally four round trips on weekdays and two round trips on weekends and public holidays.
From the Komaba Bus Stop or Chuo Expressway Hirugami Onsen Bus Stop, the hot spring area is approximately 10 minutes away by car. Some highway buses operating on the Nagoya–Iida route also travel via Hirugami Onsen.
Hirugami Onsen offers much more than a place to take a hot bath. Its highly alkaline sulfur spring, peaceful streets, local morning market, seasonal flowers, mountain scenery, and extraordinary night skies create a uniquely varied destination in southern Nagano.
Whether you visit in spring to see the hanamomo blossoms, relax in a hot spring after exploring the mountains, sample local specialties at the morning market, or travel to the highlands to gaze at a sky filled with stars, Hirugami provides an opportunity to experience the natural beauty and traditional culture of the Japanese countryside at a relaxed pace.