Inn of Kosen Karasawa Yatsugatake secret hot spring
唐沢鉱泉 八ヶ岳秘湯の宿からさわこうせん やつがだけひゆのやど
Day Use
YesClosed for winter, roughly mid-January to early April, due to snow. Day bathing runs 10:00 to 15:30, with reception closing at 15:00.
Adult day bathing is 1,100 yen, child 550 yen; a rental towel isn't included, though a towel can be bought for 550 yen. The packaged day-trip plans, 5,500 to 7,700 yen with lunch and a ride to Chino Station, do include a loaned bath towel.
Bathing & Water
Open-air outdoor bath
Google's editorial summary calls this an 'indoor & outdoor soaking pools' inn, but the site's own detailed enumeration of bath types (one shared indoor bathhouse with big windows onto the forest, no 露天 mentioned anywhere across 10 crawled pages) implies a single indoor bath only — kept the site's more authoritative, detailed account over the lower-trust Google editorial blurb.
Enclosed indoor bathing area
Dry heat sauna room
Google's editorial summary mentions a sauna, but no page on the official site (including the detailed bath-type enumeration) mentions サウナ anywhere — kept the site's silence over the lower-trust Google editorial claim.
Capabilities
Private onsen bath in guest rooms, for overnight guests only
The room-equipment list has no bath item (bathing is listed separately under building-wide facilities, 'お風呂'), implying guest rooms have no private onsen bath.
Shared bathing area for all genders
Policies & Services
Welcomes children and families
Detailed pricing tiers for elementary-school-age, preschool, and infant guests (infants 0-2 free) show the inn is set up for family stays; site also mentions school mountain-climbing group trips.
Restaurant or dining open to visitors (not just hotel meal plans)
Towels available to rent or borrow
Rental bath towel is included only in the packaged day-trip plans (お疲れ様プラン etc.); plain walk-in day bathing does not include a towel and instead sells one for 550 yen (売りタオル１枚 ５５０円).
Relaxation space for after bathing
On-site or nearby parking available
Views
Forest
MountainsHighlights
Utaseyu
Lukewarm BathPrograms
About
Karasawa Kosen is the only building in its fold of the Yatsugatake foothills, used by climbers as a jumping-off point onto the range. The bath is one shared, stone-and-wood room split by gender: a large tub and a smaller one, a lukewarm side and a hot side, a basin in the middle, and a waterfall-style utaseyu that drops the cold spring water straight off a boulder, unheated. The source itself is a cold carbonated mineral spring: tiny bubbles cling to the skin once you're in, and on a few days most years, usually around June, the normally clear water turns milky white for reasons nobody at the inn can fully explain. Big windows look onto the forest and the ridge of Tengu-dake. It's a member inn of Nihon Hitou wo Mamoru Kai (日本秘湯を守る会), the association for hideaway hot-spring inns, and appears in the book 日本の秘湯 (Nihon no Hitou), 'Japan's Hidden Hot Springs': a quiet one-building stop before or after a climb.
Loading map…
No reviews yet
Be the first to share your experience!
Last updated July 22, 2026