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Hot Springs

Kawayu Onsen is a Mt Io acid spring that is rare in Japan and has its source in the basement of Mt. Iou.

The name of Kawayu is a translation of the Ainu Language Seseki (hot) Betsu (river)", and a hot spring river flows through the hot spring town.
We have a "Gensen Kakenagashi Sengen (Take the source as it is the bath) free-flowing hot springs", and all hot springs are 100% free-flowing hot springs.
Please enjoy a very valuable real hot spring with abundant amount of hot water and no heating, watering, circulation or chlorine disinfection.

The hot spring tank is a 100% fresh source, completely discharged

An acidic sulfur spring with a pH of 1.7 is used in the hot spring bath of the large communal bath as a complete discharge type.
It is said to be effective against chronic skin diseases, chronic women's diseases, cuts, diabetes, and hypertensive arteriosclerosis.
There is also an open-air bath and a sauna.
  • About Kawayu Onsen

    Lake Mashu's largest Kawayu Onsen

    Kawayu Onsen is Mt Io and has a spring quality peculiar to Japan (volcanic).
    Kawayu Onsen, which is a bright and green hot spring containing strongly acidic hydrogen sulfide, is one of the few hot springs in Japan that is extremely valuable from a medical point of view.
    The unique spring quality and topographical environment stimulate the body with chronic illness,
    It is recognized to regulate the functions of the autonomic nervous system and hormone secretory system to enhance the ability to cure illness.

    Kawayu’s Bath reputation for being warm from the core of your body and difficult to cool.
    It is popular not only for lodging but also for day trip hot springs.It is a perfect hot spring to heal your daily fatigue.

    In addition, an experiment conducted the other day Kawayu Onsen has a considerable bactericidal effect.
  • Large communal bath

  • Large communal bath open-air bath

  • sauna

  • One-day hot spring

    Although it is a short time, we also accept day trip hot springs.
    Please enjoy the famous hot spring Kawayu Onsen
    *It will be open from May 7, 2021.

    *Rental towel (bath face) 100 yen each
    *One-day hot springs may be canceled during times of congestion such as long holidays.
    *The affiliated store "Kinkiyu Hotel" is open from 13:00 to 21:00.
    Hot spring bath hours
    From 13:00 to 15:00(16:00 Leave)
    Usage fee
    Adult(s):1,500 yen/Elementary school-aged children:1000 yen/Infants:700 JPY

Hot spring information list

Hot Springs

Kawayu Onsen (100% natural hot spring)*Does not include artificial hot springs.

Open Air Bath

Yes (both men and women (including time change), cannot be reserved)

Type of bath

Hot spring/Open-air bath/Natural Hot Springs

Number of baths

[Open-air bath]Man:1 woman:1 Mixed bathing:0
[Indoor bath]Man:2 woman:2 mixed bathing:0
[sauna]Man:1 woman:1 Mixed bathing:0

Other bath facilities


Hot spring tax

Hot spring tax Adults 150 yen will be charged separately.


【Old】Acidic alum green alum spring
【new】Acidic/Sulfur-containing/Iron (II) -sodium-sulfate/Chloride spring/colorless/Strong acidity/Hydrogen sulfide odor

Hot Spring Qualities

Acidic/Sulfur spring/Acidic Akirabansen


Hemorrhoids / Cold sensitivity / Recovery period after illness / Recovery from fatigue / Scratches / Chronic skin disease / Chronic gynecological disease / Menstrual disorders / Diabetes / Motor paralysis / Trauma / Neuralgia, etc.


Malignant tumor / Severe heart disease / Pregnant (especially early and late) / Skin / mucous membrane hypersensitivity (especially photosensitivity) / Elderly xeroderma, etc.


【ph value】1.73(Strong acid)
【Drinking permission】Yes