What Is Shima Onsen in Gunma? History, Highlights, and Why It’s Famous
Shima Onsen (四万温泉) is a historic hot spring town in Nakanojō, Agatsuma District, Gunma Prefecture, and is known as one of Gunma’s signature onsen destinations.
Its name comes from the legend that its mineral-rich waters “heal 40,000 ailments.”
There are two origin stories: one says Sakanoue no Tamuramaro stopped by during the Enryaku era (782–806), and another says Usui Sadamitsu, a retainer of Minamoto no Yorimitsu, discovered the hot spring after receiving a message in a dream in Eien 3 (989).
In 1954, it was also designated as a National Health Hot Spring Resort (Kokumin Hōyō Onsenchi), underscoring its long-standing reputation.
Set quietly in the mountains, Shima Onsen is a place where you can enjoy beautiful nature along with the nostalgic atmosphere of a traditional hot spring town.
It’s also packed with sightseeing spots—such as Sekizenkan, often said to be one of the models for the bathhouse in “Spirited Away,” and Lake Okushimako, which shines in a cobalt-blue hue.
In this guide, we’ll cover the best things to do in Shima Onsen, how to enjoy it, plus helpful travel info like access and costs.
Top Things to Do in Shima Onsen
Sekizenkan｜One of Japan’s Oldest Wooden Ryokan Buildings
The iconic Shima Onsen inn Sekizenkan is known as one of Japan’s historic wooden ryokan structures, and some of the buildings on the property are designated as cultural assets.
Founded in 1694, it’s a long-established ryokan with centuries of history.
In particular, the red bridge (Keiunbashi Bridge) over the Shima River and the main building are famous as highly photogenic spots.
Inside, you’ll find “Genroku-no-Yu,” built in 1930, a Taishō-romance-style bath with distinctive arched windows where you can enjoy free-flowing hot spring water direct from the source.
It’s also widely known for being introduced as one of the models for the bathhouse “Aburaya” in “Spirited Away,” attracting visitors from Japan and abroad.
Even if you’re not staying overnight, Genroku-no-Yu is also open for day-use bathing (around 1,500 yen).
The “Shima Blue” Clear Waters｜Lake Okushimako and Shima Lake
Shima Onsen sits in an area where the clear Shima River flows through the valley.
Especially famous is Lake Okushimako, the reservoir of the Shima River Dam, whose surface shifts between cobalt blue and turquoise depending on the light and season—known as “Shima Blue.”
Early spring is often cited as the best time to see vivid Shima Blue, when snowmelt flows into the lake.
A roughly 4 km loop road runs along the lakeshore, making it perfect for a scenic drive or cycling in nature.
In the green season, you can also enjoy activities like canoeing and SUP (stand-up paddleboarding).
You can also see Shima Blue at Shima Lake (Nakanojō Dam) near the entrance to the onsen town, so it’s a great option if you’re short on time.
Hinatami Yakushi-dō｜A Historic Hall Designated an Important Cultural Property
Located in the Hinatami area at the far end of Shima Onsen, Hinatami Yakushi-dō (日向見薬師堂) is a hall said to have been built in 1598 to pray for the lasting military fortune of the local lord Sanada Nobuyuki.
With its thatched roof and strong late-Muromachi Tang-style architectural influences, it was designated a national Important Cultural Property in 1912.
Inside, a statue of Yakushi Nyorai is enshrined, and it has long been worshipped by visitors seeking hot-spring healing as “Yuzen Yakushi.”
Right next door are the public bath “Gomusō-no-Yu,” said to be the birthplace of Shima Onsen, as well as a footbath—making this an ideal turnaround point for a stroll through the onsen town.
Public Bathhouses in Shima Onsen
Public bathhouses are scattered throughout Shima Onsen, making it easy to enjoy hot springs casually.
- Kawara-no-Yu：An open, outdoor-bath-like public bath along the Shima River.
- Gomusō-no-Yu：Next to Hinatami Yakushi-dō, known as the founding hot spring of Shima Onsen.
- Ue-no-Yu：Located mid-town, a bathhouse beloved by locals.
Soap and shampoo aren’t available at any of them, so bathing is typically limited to rinsing with hot water.
Visiting multiple baths—each with its own character—is one of the unique pleasures of Shima Onsen.
Things to Do in Shima Onsen: Activities and Experiences
Onsen Hopping
Shima Onsen has many hot spring inns of all sizes, each offering different sources and reputed benefits.
Sometimes ticket options are prepared for onsen hopping, making it a great choice if you want to try multiple baths.
The spring quality is generally described as a sodium-calcium chloride-sulfate spring, and it’s popular for leaving skin feeling smooth and moisturized.
Some places also provide drinking fountains for onsen water, and drinking the spring water may be suggested where available.
Nature Walks
There are many hiking courses around Shima Onsen where you can enjoy beautiful nature.
One standout is the “Shima no Ōketsu-gun” (pothole group), rounded holes formed over long years by river currents—designated a prefectural natural monument.
It’s also appealingly accessible, as you can reach it on foot from the onsen town.
Canoe and SUP Experiences
At Lake Okushimako, you can enjoy water activities such as canoeing and SUP.
It’s a popular way to experience Shima Blue up close, and beginner-friendly guided tours are also offered.
Experiences typically last about two hours, with the main season around May through October.
How to Get to Shima Onsen
By Train and Bus
- Get off at “Nakanojō Station” on the JR Agatsuma Line (from Tokyo, transfer at “Takasaki Station” from the Jōetsu Shinkansen; Takasaki to Nakanojō takes about 50 minutes).
- From Nakanojō Station, take the Kan-etsu Kōtsū bus bound for “Shima Onsen” for about 40 minutes and get off at the last stop.
Depending on the season, there may also be highway buses operating from Tokyo Station toward the Shima Onsen area.
By Car
- About 60 minutes from the Kan-etsu Expressway “Shibukawa Ikaho IC” via National Route 353.
- There are multiple municipal parking lots in Shima Onsen, making car access convenient.
Helpful Travel Tips for Visitors
Recommended Places to Stay
Shima Onsen has around 30 lodging options, ranging from historic ryokan to modern accommodations.
Popular choices—especially for enjoying both hot springs and cuisine—include Sekizenkan, Shima Tamura, and Shima Yamaguchikan.
Some inns also offer affordable long-stay “tōji” (hot-spring therapy) plans, making it suitable for extended visits.
Food and Local Specialties
- Street food in the onsen town：Enjoy Gunma favorites like yakimanju and onsen manju.
- River fish dishes：Try salt-grilled or tempura-style yamame and iwana made with fresh fish.
- Okirikomi udon：A Gunma comfort dish—wide noodles simmered with vegetables for a warming meal.
Best Time to Visit
Shima Onsen is enjoyable year-round, but these seasons are especially recommended:
- Spring (April to May)：Fresh greenery is beautiful, and Shima Blue often looks especially vivid.
- Autumn (late October to early November)：Fall foliage colors the onsen town and surrounding mountains, creating spectacular scenery.
- Winter (December to February)：Enjoy snowy open-air baths and a calm, atmospheric hot spring mood.
Etiquette and Safety Notes
Public bathhouses don’t provide towels or soap, so be sure to bring your own.
Many roads in the onsen town are narrow mountain lanes, so drive carefully.
Bear sightings are sometimes reported around Lake Okushimako, so carrying a bear bell or taking other precautions can be reassuring.
Summary
Shima Onsen is one of Gunma Prefecture’s premier hot spring areas, where beautiful nature and rich onsen culture come together.
With highlights like the historic Sekizenkan, the mystical Shima Blue waters, and the nationally designated Hinatami Yakushi-dō, there’s plenty to see and do.
If you’re visiting Gunma, be sure to stop by Shima Onsen and experience its charm for yourself.
Relax your mind and body, and create unforgettable travel memories.
