If any single prefecture can claim the title of Japan’s onsen capital, Gunma makes the strongest case. It holds not one but four distinct hot spring resorts of national renown, each with its own water chemistry, landscape character, and historical identity. Kusatsu draws more visitors than any other onsen town in the country. Ikaho is a century-old hillside resort with two entirely different spring types on the same street. Shima is remote, atmospheric, and haunted by association with one of Japan’s most beloved animated films. Minakami is where the mountains funnel eighteen separate hot spring sources into a single valley. Choosing between them is a genuine problem, and the only satisfying solution is to visit more than one.
Kusatsu Onsen
Kusatsu sits at 1,200 meters elevation in the mountains of northwestern Gunma, close enough to the volcanic zone to smell sulfur before you see the village. It has topped Japan’s national onsen ranking more times than any other resort.
The Yubatake
The visual and spiritual center of Kusatsu is the Yubatake, a 400-square-meter expanse of wooden water channels through which hot spring water flows continuously from its source to the town’s bathhouses. The water arrives at approximately 55°C and cools as it runs through the channels, releasing steam in cold weather and filling the central plaza with a warm sulfurous haze. Viewing the Yubatake is free and is best done at dusk when the lights come on and the steam glows.
The Water
Kusatsu’s water is highly acidic at pH 2.1, among the most acidic onsen water in Japan. This acidity is credited with strong antibacterial properties — local tradition holds that it can treat skin conditions and kill many pathogens on contact. The tradeoff is that the water is intense: it will irritate cuts or open skin, and prolonged soaking can dry out sensitive complexions. Remove metal jewelry before entering. First-time visitors sometimes find the acidity creates a mild tingling or stinging sensation, which is normal.
Public Bathhouses
All three main public bathhouses charge ¥600 per entry.
Otakinoyu is the most distinctive, offering the jikan-yu bathing ceremony — a tradition in which bathers enter a long wooden bath together and move in synchronized stages through progressively hotter sections of water. An attendant leads the session, which lasts about three minutes and involves considerable communal encouragement to keep entering hotter water. The wooden interior and ritual atmosphere make this the most memorable Kusatsu experience for most visitors.
Sainokawara Open-Air Bath occupies a large park at the eastern edge of the resort. The outdoor pool holds several hundred bathers and requires swimwear — one of the few mixed-bathing options in Japanese onsen culture. It is the right choice for couples or groups who want to soak together.
Goza-no-Yu is a more conventional indoor facility close to the Yubatake, straightforward and practical for those who want a quick, quality soak without ceremony.
Access
By bus from Takasaki Station: approximately 90 minutes. By highway bus from Shinjuku: approximately 3.5 hours, ¥3,200. The highway bus is convenient for travelers coming directly from Tokyo without backtracking through Takasaki.
Ikaho Onsen
Ikaho descends a steep hillside in a cascade of old buildings flanking a central staircase of 365 stone steps. The resort dates to the Meiji era and earlier, and its lanes retain the worn, slightly nostalgic quality of a place that has not been over-restored.
Two Spring Types
Ikaho’s defining quirk is that it offers two completely distinct spring waters within the same town. The golden water is iron-rich, turning a distinctive orange-brown upon contact with air due to oxidation. It is considered highly therapeutic, particularly for fatigue and skin conditions, and has a warming, almost metallic quality. The silver water is clear and gentler, with a neutral mineral profile suited to sensitive skin or first-time onsen visitors.
Some ryokan pipe both types to guest rooms, allowing guests to compare them in adjacent baths. If yours offers this, take the opportunity — the difference is immediately apparent.
The 365 Steps
The stone staircase is lined with small shops, food vendors, and a few traditional game stalls, giving it the feel of a Japanese festival street stretched vertically. Vendors sell Mizusawa udon, shotoku ice cream, and Gunma souvenirs at intervals up the climb. At the top stands Ikaho Shrine, a quiet space amid cedar trees that rewards the effort.
Descending the steps in the afternoon, when the light falls on the old wooden buildings, makes for some of the best street photography in Gunma.
Access
Bus from Shibukawa Station: approximately 30 minutes. Shibukawa is on the JR Joetsu Line from Takasaki (about 20 minutes).
Shima Onsen — The Spirited Away Connection
Shima Onsen occupies a narrow mountain valley about 1.5 hours from Takasaki by car, accessible only by winding mountain roads. The remoteness is part of the appeal. The valley holds a small river, a cluster of ryokan, and an atmosphere of genuine isolation from the modern world.
Sekizenkan — Japan’s Oldest Ryokan
The most famous building in the valley is Sekizenkan, established in 1691 and operating continuously ever since. The oldest section of the building — a red bridge over the river leading to a multi-story wooden structure with deep eaves and traditional lattice windows — is widely cited as one of the inspirations for the bathhouse in Hayao Miyazaki’s animated film Spirited Away. The connection is unofficial but visually unmistakable.
Staying at Sekizenkan is an experience in itself. The rooms in the original building are small and atmospheric; the baths are fed by spring water channeled from the mountainside. The service follows classical ryokan protocols: yukata robes, multi-course kaiseki dinner, and a formality that feels appropriate to a building of this age. Room rates start around ¥15,000 per person including dinner and breakfast.
Even visitors not staying at Sekizenkan can cross the red bridge and photograph the exterior, and day-bathing is sometimes available for a fee — check directly with the ryokan when planning.
Getting There
There is no convenient public transport to Shima Onsen. A rental car from Takasaki or Nakanojo Station is the practical option. The drive through the mountain valleys takes approximately 1.5 hours from Takasaki. Some ryokan offer pickup service from Nakanojo Station; inquire when booking.
Minakami Onsen
Minakami sits in the northernmost corner of Gunma, where eighteen separate hot spring sources emerge from the surrounding mountains and flow into a single valley. The variety means that different ryokan within the same town can offer distinctly different water — some clear and lightly mineral, others milky or faintly sulfurous.
Onsen and Adventure
Minakami is unusual among Japan’s onsen resorts in that it has built a parallel identity as an outdoor adventure destination. The Tone River, which flows through the valley, provides Class III and IV whitewater for rafting from late April through October. Canyoning in the side gorges is available through several outfitters. It is entirely possible to spend a morning rafting, eat lunch in town, and soak in an onsen by late afternoon — a combination that few other resorts in Japan can offer.
Access
JR Joetsu Line from Takasaki to Minakami Station: approximately 50 minutes. From Minakami Station, most ryokan offer shuttle service, or the town is walkable and bikeable.
Choosing Your Gunma Onsen
| Resort | Atmosphere | Water Type | Best For | Access from Takasaki |
|---|---|---|---|---|
| Kusatsu | Lively, established | Highly acidic (pH 2.1) | First-timers, solo travelers | 90 min bus |
| Ikaho | Traditional, scenic | Iron-rich golden / clear silver | Couples, photographers | 50 min (train + bus) |
| Shima | Remote, historic | Mountain mineral spring | Ryokan experience, atmosphere | 1.5h by car |
| Minakami | Active, scenic | Varied (18 sources) | Couples, adventure travelers | 50 min by train |
Onsen Etiquette for First-Timers
Onsen etiquette is not complicated, but it is important to know in advance.
Wash before entering. Every onsen facility provides shower stations beside the baths. Wash your entire body with soap and rinse thoroughly before stepping into the communal water. This is non-negotiable.
No swimwear in indoor baths. Traditional indoor onsen are entered without clothing. Sainokawara in Kusatsu is an exception as an outdoor mixed bath requiring swimwear; check individual facilities.
No towels in the water. Small towels can be carried in and used to cover yourself while walking, but they should not be submerged. Fold or place them on your head while soaking.
Tattoos. Many onsen facilities in Japan prohibit entry for guests with visible tattoos. This policy varies and is slowly changing at tourist-oriented resorts, but it is wise to check in advance. Private baths (kashikiri-buro), available at most ryokan for an additional fee, have no such restrictions.
Hair. Long hair should be tied up to keep it out of the water.
Hydration. Onsen water, especially Kusatsu’s acidic variety, is dehydrating. Drink water before and after soaking. Most facilities sell canned drinks and cold water at the exit.
Practical Tips
Booking ryokan: Gunma’s popular ryokan, especially Sekizenkan and well-regarded Kusatsu properties, book out weeks or months in advance on peak weekends and during autumn foliage season (mid-October). Book as early as possible through the ryokan directly or through services such as Jalan or Rakuten Travel, which accept international credit cards.
Day trips vs. overnight stays: Kusatsu and Ikaho can be visited as day trips from Tokyo, but the experience is significantly richer with an overnight stay. The ryokan dinner, the morning bath before other guests are awake, and the quieter atmosphere after day-trippers leave are all reasons to stay.
Combining resorts: Kusatsu and Ikaho are in different parts of Gunma and are not easily combined in a single day by public transport. With a car, a two-day itinerary can cover both plus Shima or Minakami.
Winter visits: All four resorts are open year-round. Kusatsu has a ski resort (day pass ¥4,500) and is particularly atmospheric in snow. Ikaho and Minakami are less crowded in winter and offer discount room rates at many ryokan.