A Long History Connected to the Kumano Pilgrimage
The origins of Tsuboyu are said to date back to ancient times. According to tradition, the hot spring was discovered around the 4th century. By the Nara and Heian periods, Yunomine had already become a well-known hot spring destination.
Its reputation spread throughout Japan through the Kumano Kodo pilgrimage, particularly as retired emperors, members of the imperial family, aristocrats, and other pilgrims traveled to the sacred sites of Kumano. Before and after visiting Kumano Hongu Taisha, one of the three major shrines of Kumano, pilgrims would stop at Yunomine to cleanse their bodies and refresh themselves after their journey.
The custom became an important part of the pilgrimage tradition. So many people eventually traveled toward Kumano that the pilgrimage was described with the expression “the pilgrimage to Kumano like ants”, reflecting the seemingly endless stream of worshippers making their way through the mountains.
The Traditional Atmosphere of Yunomine Onsen
Yunomine Onsen is a quiet hot spring settlement surrounded by the mountains of the Kii Peninsula. Its narrow streets, traditional buildings, steaming waters, and peaceful natural surroundings create an atmosphere reminiscent of an old Japanese therapeutic bathing village.
Along the Yunomine River, a small building stands quietly beside the flowing water. This is Tsuboyu. Although its appearance is simple, its historical and spiritual significance makes it one of the most distinctive hot springs in Japan.
A Small, Rustic Bath Built Beside the River
Tsuboyu is housed in a small, mountain hut-like structure beside the river. Inside is a bathtub carved from natural stone, giving the bath a remarkably rustic appearance.
The bathing space is very small and can accommodate approximately two adults at a time. There is only a simple area for changing clothes, and the facilities are intentionally kept modest. The use of soap and shampoo is prohibited in the bath, helping preserve the natural environment and the traditional character of this historic hot spring.
A Mysterious Natural Hot Spring
The Enigmatic Changing Colors of the Water
One of Tsuboyu’s most fascinating characteristics is the mysterious changing color of its water. The water may appear clear at one moment and then take on a milky or slightly bluish appearance at another time.
There is a traditional saying that the color of the water changes seven times in a single day. Although the actual appearance depends on natural conditions and changes in the spring water’s mineral composition, this phenomenon adds to the sense of mystery surrounding Tsuboyu.
Because the water can look different depending on the time and conditions, each visit can provide a slightly different experience.
The Spring Emerges Naturally from Beneath the Bath
Tsuboyu is a naturally flowing hot spring, with the spring water rising directly from beneath the stone bath rather than being pumped into it. The surrounding Yunomine River area is also known for numerous natural springs.
In some places around the river, visitors can even see bubbles rising from the riverbed, offering a vivid reminder of the geothermal forces beneath the mountains. This close connection with nature is an important part of the appeal of Yunomine Onsen.
Hot Spring Properties and Traditional Benefits
The spring water is a sulfur-containing bicarbonate spring with chloride and sodium components. Its source temperature is approximately 92.5°C, making it far too hot to enter directly at the source. The bathing water naturally cools as it emerges and reaches the bath.
Historically, the waters of Yunomine have been valued as a kind of medicinal bath. Traditional bathing culture associated the spring with benefits such as relief from fatigue, neuralgia, rheumatism, and certain skin conditions. These traditional claims form part of the long history of the hot spring, although they should not be regarded as modern medical treatment.
How to Experience Tsuboyu
A Private Bathing Experience
Tsuboyu is operated on a private-bath system, with each group given approximately 30 minutes to use the bath. Visitors receive a numbered ticket at the nearby Yunomine public bath and wait for their turn.
Because only one group can use Tsuboyu at a time, the experience is much more private than a typical Japanese public bath. This allows visitors to enjoy the small stone bath and its natural surroundings in a peaceful atmosphere.
Tsuboyu is extremely popular, especially during weekends, holidays, and peak travel seasons. Waiting times can therefore be considerable. Visitors are encouraged to allow plenty of time in their itinerary rather than planning a tightly scheduled visit.
Enjoying the Public Bath as Well
Visitors who use Tsuboyu can also enjoy the nearby Yunomine Onsen public bath. This provides an opportunity to experience another aspect of the area’s traditional bathing culture.
The public bath offers different bathing options, including “Ippon-yu,” in which the temperature is adjusted by adding water, and “Kusuri-yu,” which uses the hot spring water in a more natural state. Experiencing both facilities allows visitors to appreciate the diversity of Yunomine’s bathing traditions.
There is also a place where visitors can collect hot spring water, allowing them to take a small amount home and enjoy another aspect of Yunomine’s famous natural waters.
More Than Just a Hot Spring
Tsuboyu is much more than a place to relax in hot spring water. It is a remarkable destination where history, spirituality, pilgrimage culture, and nature come together.
For travelers walking the Kumano Kodo or visiting the sacred sites of the Kumano region, bathing at Tsuboyu provides an opportunity to physically experience a tradition that has continued for centuries. The act of bathing is connected to the ancient practice of purification, giving the experience a deeper cultural meaning than an ordinary visit to a hot spring.
The cultural importance of the area has also encouraged efforts to protect its natural environment and traditional landscape. Preserving Yunomine’s historic atmosphere while welcoming visitors is an important part of maintaining this unique destination for future generations.
Access to Tsuboyu
Tsuboyu is located in the Yunomine Onsen area of Tanabe City, Wakayama Prefecture. From JR Kii-Tanabe Station, the journey by bus takes approximately 90 minutes. Get off at the Yunomine Onsen bus stop, from which Tsuboyu is only a short walk away.
The journey itself takes travelers deep into the mountainous landscape of the Kii Peninsula. Surrounded by forests, rivers, and quiet mountain scenery, Yunomine Onsen provides a peaceful contrast to Japan’s larger cities and busy tourist destinations.
A Unique World Heritage Experience in Japan
Tsuboyu is an exceptionally rare destination: a historic hot spring that is part of a UNESCO World Heritage site and can still be used for bathing today. Its approximately 1,800-year-old history, connection with the Kumano pilgrimage, naturally flowing hot spring water, and intimate stone bath make it unlike almost any other bathing experience in Japan.
For international visitors, a visit to Tsuboyu offers more than simply soaking in a hot spring. It is an opportunity to experience the relationship between Japanese spirituality, pilgrimage traditions, and the natural landscape of the Kii Peninsula.
The quiet atmosphere of Yunomine Onsen, the mysterious appearance of the spring water, and the centuries of history associated with Kumano create an unforgettable experience. For travelers exploring the Kumano Kodo and the sacred sites of Kumano, Tsuboyu is a unique destination well worth including in their journey.