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Isazen Inn

いさぜん旅館いさぜんりょかん

Lodging

Day Use

Yes
10:00–18:00

Bathing & Water

Natural onsen water

Uses natural hot spring water

Indoor BathYes

Enclosed indoor bathing area

Bathing Arrangements

Mixed BathingYes

Shared bathing area for all genders

Policies & Services

WashingYes

Shower, wash stations, soap and shampoo provided

Water treatment

Pure source water· 源泉かけ流し (gensen kakenagashi)
from Article 18 disclosure
  • Added water
    No
  • Reheated
    No
  • Recirculated
    No
  • Disinfected
    No
  • Bath additives
    No

新井第2号泉・動力揚湯源泉、新井第5号泉・唐竹沢源泉 混合泉

Arai Spring No.2 / Arai Spring No.5 (Karatakezawa) Blended Source

Operated by · 東鳴子源泉管理有限会社

Mixed source

曹
Bicarbonate
+ Chloride
Color
colorless and transparent
Taste
tasteless
Odor
odorless

Sodium Bicarbonate-Chloride spring

pH 8.2Weakly alkalineHot source · 64°C
Composition fingerprint1.4 g/kg dissolved · Hypotonic
Na⁺83
HCO₃⁻61
Cl⁻22
SO₄²⁻17
◀ CationsAnions ▶
Sodium Na⁺
salt's cation — pairs with chloride to make the water salty.
Bicarbonate HCO₃⁻
"soda" — softens skin, leaves it smooth.
Known good for
  • Smooth skindry, rough skin
  • Aches & jointsstiff shoulders
  • Warmingcold sensitivity

A hot (64 degC) blended source combining Arai Spring No.2 with the Karatakezawa Spring (Arai No.5). The chemistry is a sodium bicarbonate-chloride water — bicarbonate-led with a salty layer underneath — weakly alkaline and soft on the skin, of the classic beauty-water family. Metasilicic acid runs to a generous 237 mg/kg, leaving the kind of fine silica film that makes skin feel noticeably smoother afterwards.

Sampled at mixing tank·Analyzed Jul 10, 2023·公益財団法人 宮城県公害衛生検査センター·Cert no. 公衆検第1246号

Explore the water

About

An old-style inn in the Tohoku mountains where the mixed communal bath (いさぜんの湯) draws water from multiple sodium bicarbonate springs. The water is soft and slightly alkaline, well-suited for longer therapeutic stays, the inn has a shared kitchen for guests doing a proper hot-spring cure. Day-bathing is available.

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1 review

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Sergey M
1 year ago· edited

227. Isazen Inn, Naruko Onsen, Miyagi I went for a day trip, it said 2 stamps, but I remember they took 3, I think (listed from 10:00 to 18:00). There were as many as four signs in the hallway and an old massage chair. Overall, the place feels like something out of an anime. Indoor bath. It is comfortable to breathe. The bottom and walls of the bath are black and red, so the bath looks rugged. In fact, the water is clear, and the temperature is 42. Very slippery in the bath. 06.11.2024

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Last updated October 15, 2026