The Numajiri Motoyu, the source area of Nakanosawa Numajiri Onsen, is located halfway up Mount Adatara (about 1,300 meters above sea level) on the mountain trail from the Numajiri trailhead. It boasts the highest volume from a single hot spring source in Japan at 13,400 liters per minute. Because of the abundance of hot water, the hot spring turns into a river for about 500 meters, and you can experience a rustic open-air bath in the source area. Also, on the way to Numajiri Motoyu, you can see a hot spring waterfall (Shiraito Falls) and a cave hot spring where hot water flows, which you can enjoy before reaching the source. In accordance with the plan to improve the source area launched in April 2020, the work road that runs parallel to the trail can be used as a path, and the general public is now able to visit the source with a guide to ensure safety. The content of the experience is planned to be the Numajiri trailhead, the work path, Shiraito Falls, a picturesque spot above the falls, the cave hot spring, and an outdoor experience at the hot spring source area.

Course Content: Mount Adatara Numajiri trailhead, work path, (10 minute travel time), Shiraito Falls view point (10 minute visit), (15 minute travel time), picturesque spot above the waterfall (10 minute visit), (5 minute travel time), cave hot springs (30 minute bathing time available upon request), (10 minute travel time), open-air bath at the hot spring source area (45 minute bathing time)  [Time required: about 2.5 hours]

Highlight 1: "Shiraito Falls view point" of a hot spring waterfall with a drop of about 60 meters. Depending on the season, you can enjoy the picturesque view of fresh greenery, dark green and autumn foliage.

Highlight 2: "Picturesque spot above the waterfall," a viewing platform above the waterfall with expansive superb scenery below you. Depending on the weather, you can see Aizu Mount Bandai and Urabandai.

Highlight 3: "Cave hot spring," featuring a cave where hot water flows that you can bathe in if you would like. This is an Instagram-worthy spot that is rarely seen in the world.

Highlight 4: "Open air hot spring," where you can bathe in a rustic bath at the confluence of the hot spring river from the source and the natural river. This area has an abundance of hot spring mineral deposits, so when you stir the riverbed, the pure white cloudy water gives you the full hot spring feeling. As the name "Extreme Onsen" implies, this is a completely new hot spring area where you can have a uniquely superb active experience. The surrounding landscape created by nature has a unique atmosphere, and the vast hot spring area in the valley is stunning. Bathing in the open-air hot spring while appreciating the blessings of nature is an overwhelmingly extraordinary experience. There is no doubt that this will be popular among inbound tourists, especially active people from Europe and the United States.