Tenjinonsen Seiunso

The bath here draws on a carbonated cold spring, one of the rarer types found in Japan, warmed before use since it comes up cold from the ground. There's one indoor bath each for men and women, redone in 2014, kept plain rather than fancy, in keeping with the inn's simple, old-style feel. Above the bath, Seiunso is a public lodge (国民宿舎) up in the Kiso Koma highlands: ten tatami rooms sharing a communal bath and toilet, a large multipurpose hall, and a dining room with a charcoal-grill house, though as of 2026 overnight stays are room only, with no meals included. The spring itself was found by accident in 1989, when the owner's daughter, playing in the Masazawa river that runs past the inn, spotted bubbles rising from the riverbed. Digging behind the building struck a source about 100 meters down. It's named Tenjin for a shrine tied to the local warlord Kiso Yoshinaka, paired with Kiso Koma for the highland it sits in.