Akayu Onsen Kozanso
赤湯温泉 好山荘あかゆおんせん こうさんそう
Day Use
YesOpen late November to mid-April (seasonal operation)
Adults ¥700, children ¥300
Bathing & Water
Uses natural hot spring water
Open-air outdoor bath
Enclosed indoor bathing area
Capabilities
Private onsen bath in guest rooms, for overnight guests only
Official room-count table shows 0 rooms with private open-air baths.
Shared bathing area for all genders
Policies & Services
Welcomes children and families
Restaurant or dining open to visitors (not just hotel meal plans)
Shower, wash stations, soap and shampoo provided
On-site or nearby parking available
Views
Mountains
ForestPrograms
About
Kozanso (好山荘) sits alone in a beech forest on the Adatara mountain range, with two completely different springs running in separate baths. The indoor bath fills with iron-rich water that runs a deep amber-red; the open-air bath a short walk away holds cloudy sulfurous water. Both flow kakenagashi. The inn was rebuilt after earthquake damage in 2021 and reopened to guests, and is a member of Nihon Hito wo Mamoru Kai (日本秘湯を守る会), the association of remote hot-spring inns. It opens from mid-April through late November.
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Last updated July 22, 2026