Extreme Onsen

A new-style trekking with a visit to the natural hot spring source

Nearby Ryokans

What Is the “Extreme Onsen” at Numajiri Onsen Motoyu?

Located in Inawashiro Town, Fukushima Prefecture, Numajiri Onsen offers a unique outdoor adventure called the “Extreme Onsen” — a new-style tour that combines trekking with a visit to the natural hot spring source.

This guided tour takes participants on about an hour-long mountain trek toward the Numajiri Onsen Motoyu, which springs from the mountainside of Mt. Adatara at an altitude of around 1,300 meters. With an incredible discharge rate of 13,400 liters per minute, Numajiri’s spring boasts the largest single-source flow in Japan. The abundant hot water streams down through a valley, forming rustic open-air baths surrounded by untouched nature.

café&activity nowhere, a renovated former ski lodge now serving as a café and activity center, offers numerous experiences that highlight the local nature and history, including the “Extreme Hot Spring.”

Originally, this area was a historic hot spring region with over 200 years of history since the Edo period, and it also served as a mountain resort featuring the oldest ski area in the Tohoku region. However, due to the effects of sulfur gas and other natural conditions, the inns that once stood around the Numajiri Yumoto area have disappeared. Today, the area is accessible only through guided tours.

Highlights of the Extreme Hot Spring

The “Extreme Hot Springs” tour, departing from the activity center “café&activity nowhere,” offers views of the Adatara Mountain valley covered in deep greenery, where the Shiraito Falls cascade down steep cliffs, creating a magnificent landscape.

Walking along the mountain path bathed in dappled sunlight, we proceed while listening to the guide’s explanations about plants and the terrain. After about 30 minutes, the scent of sulfur gradually fills the air. Soon, the valley opens up, and you arrive at the valley floor where steam rises from the hot spring source beneath your feet. The hot spring water flows strongly through the valley like a river, with some spots reaching temperatures close to 60 degrees Celsius. Surrounded by rocks and isolated from the outside world, the space offers a breathtaking view: the contrast between the blue sky, the green mountainside, and the slightly bluish milky white water is truly spectacular.

The bath is deep enough to soak up to an adult’s chest, offering a wild sensation of surrendering to the earth’s blessings. This hot spring experience is exclusively available by reservation only, limited to two groups (maximum eight people) per day, providing a special plan to bathe without concern for others in the midst of nature.

Savor the aromatic “Hishi Tea” made from roasted water chestnuts from Lake Inawashiro, or enjoy sasa dumplings wrapped in bamboo leaves and filled with mugwort, all while being enveloped in the scent of sulfur and warming your body to the core.

How to Enjoy / Recommended Activities

This tour runs annually from May to November. At an elevation of about 1,300 meters, it’s high up, so even in midsummer, temperatures are 7–8°C cooler than in lowland areas, making it very comfortable. If you’re fed up with the sweltering summer heat in the city, why not escape to the “Extreme Hot Springs” for a summer retreat?

We recommend staying at the adjacent Numajiri Kogen Lodge the night before your tour. Enjoy a carefully prepared dinner and the natural hot spring baths, preparing yourself for the next day’s tour.

Departures are available in morning and afternoon sessions (9:00 AM–12:00 PM / 1:00 PM–4:00 PM). Participating in the morning session allows for a more relaxed schedule after descending the mountain. For trekking, you’ll need clothing suitable for hiking, non-slip shoes, and bathing essentials such as swimwear and a towel.

After descending the mountain, enjoy locally sourced coffee at the café “café&activity nowhere” or browse their original goods and souvenirs. Guests staying at “Numajiri Kogen Lodge” can als

Basic Information

Hours: Saturdays, Sundays, and national holidays — 10:00 a.m. to 3:00 p.m.
(Food last order: 2:00 p.m. / Drinks last order: 3:00 p.m.)

(Food last order: 2:00 p.m. / Drinks last order: 3:00 p.m.)Fee: Group-based pricing (varies by number of participants)
e.g. 1 person ¥24,200 / 2 people ¥13,750 per person / 3 people ¥9,900 per person / …
8 people ¥6,600 per person