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Kusatsu Onsen

草津温泉くさつおんせん

Public Bathhouse
Chubu·Yamanashi

Day Use

Yes
06:00–22:00
¥470

Bathing & Water

Natural onsen water

Uses natural hot spring water

Outdoor BathYes

Open-air outdoor bath

Indoor BathYes

Enclosed indoor bathing area

Cold BathYes

Cold water plunge bath, typically used after sauna

Policies & Services

WashingYes

Shower, wash stations, soap and shampoo provided

Soap is available

草津温泉

Kusatsu Onsen

Operated by · 有限会社 草津温泉

Chloride
Color
colorless and transparent
Taste
tasteless
Odor
odorless

Sodium Chloride spring

pH 8.1Weakly alkalineHot source · 47°CHigh silica
Composition fingerprint1.3 g/kg dissolved · Hypotonic
Na⁺92
Cl⁻76
HCO₃⁻14
CationsAnions
Sodium Na⁺
salt's cation — pairs with chloride to make the water salty.
Chloride Cl⁻
table-salt anion — coats the skin and holds heat in.
Known good for
  • Warmingcold sensitivity
  • Aches & jointsstiff shoulders
  • Smooth skindry, rough skin

A sodium chloride spring — salty and heat-retaining, drawn hot at 47.3 °C. Weakly alkaline and soft on the skin, it carries a generous 168 mg/kg of metasilicic acid, leaving the kind of thin silica film that makes skin feel noticeably smoother afterwards. Colorless, tasteless and odorless at the source.

Sampled at wellhead·Analyzed Nov 24, 2017·株式会社 山梨県環境科学検査センター·Cert no. 山環温第29-12号

Explore the water

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4.0

1 review

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Sergey M
1 year ago

578. Kusatsu Onsen, Kofu, Yamanashi ★★ Sento with the very famous name, using onsen water, for 470 yen. Soap provided. Operating hours from 06:00 to 22:00. They stamp the Yamanashi 100 Onsen book, but the stamp is very worn out. Bath photos from the internet match reality. 1. Indoor area. Breathing inside is tolerable. 1.1. Bath with clear water, temperature around 42°C (despite the sign saying 39-41). 1.2. Bath with clear water, temperature around 46.7°C. 1.3. Cold bath. 2. Outside behind a fence — a shallow bath. Clear water, temperature around 44°C. This sento has impressively hot baths compared to others in Yamanashi, plus the amusing name (which even Japanese people find funny), and the interior design — definitely recommended for a visit. 14.05.2025

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Last updated July 3, 2026