Seseragi no Yu hot spring is located in Norikura Kogen, on the eastern foothills of Mt. Norikura in the Northern Alps, at an elevation of approximately 1,500 meters. Despite being just a 5-minute walk from the Norikura Tourism Center in the heart of the hot spring resort area, this wooden bathhouse hidden in the forest along a stream remains a hidden gem known only to those in the know.

The most remarkable feature of this hot spring is that it is one of the rare completely free public open-air baths in Nagano Prefecture. Carefully maintained by the Norikura Kogen Hot Spring Association, it operates seasonally from late April to mid-November. Originally a rustic open-air bath along the river, it has been renovated into a wooden semi-open-air bath facility.

The source spring, Yukawa Onsen, is located at approximately 2,000 meters elevation on the slopes of Mt. Norikura. The milky white simple sulfur spring water is piped down to the bath, creating an authentic hot spring experience with the distinctive hydrogen sulfide aroma and abundant mineral deposits floating in the water. The baths are gender-separated, each accommodating only 2-3 people, but the intimate setting allows bathers to enjoy the sounds of the nearby stream.

Historically, the hot springs of Mt. Norikura are said to have naturally emerged from the Ohhi silver mine developed by the warlord Takeda Shingen, who reportedly used these waters to heal his fatigue. Today, it continues to be cherished by mountain climbers, tourists, and locals as a valuable part of the Norikura hot spring resort complex.