Exploring Gunma's Onsen Culture

One of the world’s most famous hot spring areas, the hot, mineral-rich waters of Kusatsu Onsen have welcomed everyone from warlords and warriors to weekend tourists for over a thousand years. While the origins of the hot springs here are lost to history, records show that Minamoto no Yoritomo (1147–1199) the first shogun of the Kamakura shogunate, bathed in the springs when hunting in the area. Distinguished by the yubatake, a hot spring that gushes from the ground in the center of the town, Kusatsu Onsen was a lively destination for bathers in the Edo period (1603–1868) and it was said that Tokugawa Yoshimune (1684–1751), the eighth shogun of the Tokugawa Shogunate, had spring water from Kusatsu carried to Edo Castle for his own use.

Kusatsu Onsen gained international acclaim when Dr. Erwin von Bälz (1849–1913), an advisor physician to the imperial family, heralded Kusatsu Onsen as a world-class hot spring resort. In 1904 he wrote, “In addition to its unrivalled hot springs for baths, Kusatsu has the best mountain air in Japan and splendid water for internal use.”

The acidic spring waters of Kusatsu are known for their healing and anti-bacterial properties, and “cure any ailment except heartache.” The pH value of the springs, which indicates the degree of acidity, is 1.6 to 2.1 (7 is neutral) and acts as a powerful disinfectant, killing most bacteria and harmful microorganisms within seconds of exposure. Kusatsu has the largest natural output of any hot spring in Japan. More than 32,300 liters of spring water gush out every minute from the main sources: Yubatake, Sainokawara, Bandai, Shirahata, Jizo, Nikawa, and others. The waters contain sulfur, aluminum sulfate, and chloride, which have antibacterial and anti-inflammatory properties, ideal for soothing skin conditions, neuralgia, and aching muscles. The acidic water can erode metal, so it is essential to remove any metal jewelry or accessories before bathing.

Yubatake is the symbol of Kusatsu, at the center of the town. Hot, milky-green water from the spring's source gushes down wooden channels made from thick pinewood, and at night the steaming hot spring is illuminated, creating a magical atmosphere. Yu-no-hana ("sulfur flowers" or mineral salts) form as the spring water is exposed to the air. This mineral-rich sediment is a popular souvenir to recreate a Kusatsu bathing experience at home.

The onsen town has a large selection of accommodations with onsen baths, ranging from traditional inns to modern hotels. Three popular baths to try are Sainokawara Open-Air Bath, Otakinoyu, and Gozanoyu. Bathe in the fresh air at Sainokawara, an open-air bath (rotenburo) fed by the Bandai springs. The large bath is separated for men and women. Otakinoyu is a charming wooden bathhouse where you can try traditional awase-yu bathing culture, where several baths are taken in turn, each hotter than the last. Gozanoyu is an elegant reconstructed bath facility that combines both Edo- and Meiji-period styles. The two stone and wooden baths are filled from the Yubatake spring with acidic sulfur and Bandai spring with acidic chloride sulphate. Enjoy the different sensations on the skin between the two baths.

Ikaho Onsen has a history stretching back to before 759 CE, when it was mentioned in the Manyoshu, Japan's oldest surviving collection of poems. The hot springs are believed to have formed before 600 CE, released by the volcanic eruption of nearby Mt. Futatsu. Ikaho Onsen served as a sanatorium for samurai after the Battle of Nagashino in 1576, and has enjoyed a reputation for healing ever since. The town is arranged around the ishidan, a central set of 365 Stone Steps which have been a symbol of Ikaho Onsen for over 400 years. Ikaho Onsen is easy to access from Maebashi and Takasaki.

Ikaho has two types of spring water, Kogane no Yu ("golden water"), where high iron content gives the water a brownish-red hue, and Shirogane no Yu ("silver water"), which comes from a newly discovered spring. Kogane no Yu is a sulfate hot spring, which flows out colorless, before turning a warm brown on exposure to the air, due to the iron content in the water. The water is said to improve circulation, alleviate muscle pain, arthritis and neuralgia, and improve conditions like hypertension and stress. Shirogane no Yu is a mild hot spring with silicic acid, which is recommended for recovery from fatigue and convalescence from illness. Try both types of spring water to compare their properties.

There is a wide range of onsen baths to try in Ikaho, ranging from traditional inns and outdoor baths, to modern facilities. Ikaho Open-Air Bath is one of the most famous public baths in Ikaho, drawing its waters directly from the Kogane no Yu spring. You can enjoy the seasons as you relax in the open air. There is a drinking fountain on the way to the bath house, where you can taste the healing golden water.

Ishidan no Yu is a traditional onsen near the bottom of the Stone Steps, drawing from the Kogane no Yu spring. Stay overnight to make the most of your visit, and enjoy both types of hot spring. Popular accommodations include Oyado Tamaki and Moriaki Ryokan which are both close to the Stone Steps, along with Joshin-no-sato Hibikino, Kishigon Ryokan, Hotel Matsumotoro, Chigira Jinsentei, and Ikaho Shusuien.

While Kusatsu Onsen and Ikaho Onsen are famous for their healing properties, there are other, lesser-known hot spring areas which also have a long history of healing. The hot spring waters at the foot of Mt. Akagi have drawn bathers since at least 1467, according to an inscription on the guardian Buddha of Akagi Onsen. Mt. Akagi is composed of 12 mountains, encircling the beautiful Lake Onuma caldera. The area is close to the city of Maebashi, making it an ideal weekend escape. Akagi Onsen Area is said to have been popular for the healing properties of its waters since the daimyo of Maebashi built bathing facilities here for the people in the seventeenth century. Akagi Onsen Area is comprised of five inns fed by the hot springs Akagi Onsen, Chuji Onsen and Takizawa Onsen. A few days of hiking and bathing will soothe body and soul.

Ancient accounts describe animals using the healing waters of Akagi Onsen. The highly carbonated waters are rich in calcium, sodium and magnesium, believed to alleviate neuralgia, muscular pain and a host of other health concerns. The healing waters flow clear from the source at around 44 degrees Celsius, then change color as the minerals oxidize. You can often find yunohana in the onsen baths of Akagi Onsen Area, a phenomenon where the minerals crystalize on the surface of the water.

There are five onsen inns in the area, each with indoor and outdoor baths, drawn directly from the springs. Cuisine features locally sourced ingredients such as river fish, Akagi beef, tofu made with spring water, and vegetables from local farms. The mountain roads around Akagi draw cyclists from across the country for the annual Akagiyama Hill Climb, but even casual cyclists can enjoy the mountain roads and clean air. Rent an e-Bike to help you power up the hills at Prefectural Akagi Park Visitor Center, from mid-July to mid-November. In winter, when Lake Onuma on Mt. Akagi freezes over, fishing enthusiasts flock to the area to enjoy ice fishing for wakasagi, or Japanese pond smelt. Beginners are welcome, and you can rent everything you need from shops on the lakeshore, where you can also get fishing tips. At the end of the day, take your catch back to the rental shop and have it deep-fried for free.

For first timers, Gunma’s onsen waters may feel very hot. It takes some time to get used to the temperature, but the health benefits of a hot bath are well-documented. Of course, if you feel unwell or have a fever, you should not enter an onsen. Before you enter the bath, you should clean your body with soap and hot water; this ensures the bath water stays clean, but also helps your body to acclimatise to the hot water. Enter the bath slowly, and only submerge your body up to your chest, until you become used to the temperature. Don’t stay in the bath too long; around 10 minutes is a good amount for the first time. If you start to sweat a lot, it is time to leave the water. The minerals in onsen water are beneficial to the skin, so don’t rinse off the water after bathing; just pat your skin dry. Be sure to rehydrate after your bath. Most bath houses have a relaxation area, with drinks. Don’t drink the onsen water, unless there is a special drinking fountain. Get dressed or put on a yukata, and rest for about 30 minutes to allow your temperature to stabilize, before heading out. Read more about onsen etiquette.