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Tamagawa Onsen | Japan's Most Acidic Hot Spring for Healing

Published May 9, 2026·3min read

Deep in the mountains of Akita Prefecture, within Towada-Hachimantai National Park, lies Tamagawa Onsen. It boasts the most acidic spring water in Japan with a pH of 1.2, gushing out at 9,000 liters per minute. It has long been known as a special therapeutic spa, or "toji."

Table of Contents
  1. Overview
  2. Primary Spring Quality and Indications
  3. Water Characteristics and Best Season
  4. Access
  5. Nearby Sightseeing & Local Cuisine

Overview

Tamagawa Onsen is a hot spring resort located in Semboku City, Akita, within the Towada-Hachimantai National Park. Its history dates back to around 1680 when it was reportedly discovered by local Matagi hunters. Initially called "Shika no Yu" (Deer's Hot Spring), it was later renamed Tamagawa Onsen.

Its most prominent feature is its water, which at a pH of 1.2 is the most acidic in Japan. The flow rate from a single source is also the largest in the country, with 9,000 liters of hot spring water gushing out every minute from the main source called "Obuke." This highly acidic quality, combined with natural bedrock bathing that utilizes geothermal heat, has made it famous nationwide as a therapeutic spa. Visitors practice a unique bathing method by lying on woven mats over geothermally heated ground, warming their bodies with gentle heat and trace amounts of radiation.

Primary Spring Quality and Indications

Acidic

The water at Tamagawa Onsen is classified as an "Acidic spring." The highly acidic water, with hydrochloric acid as its main component, has a distinct tingling sensation on the skin. It is said to have strong sterilizing effects and is believed to be beneficial for various conditions. When bathing, it is important to follow proper procedures, such as avoiding contact with eyes and refraining from long soaks.

  • Atopic dermatitis
  • Psoriasis vulgaris
  • Chronic eczema
  • Rheumatoid arthritis
  • Peripheral circulatory disturbance

Water Characteristics and Best Season

The source temperature is a very high 98°C (208°F), and the water is used in a 100% free-flowing system. However, the bathing facilities are designed with first-time visitors in mind, offering baths with 50% source water or cooler temperatures to moderate the intensity. Due to the high acidity, it is recommended to remove any metal accessories before bathing as they may tarnish.

Tamagawa Onsen is located in a heavy snowfall area, and access roads are closed during the winter (early December to mid-April), with facilities also shutting down. The best time to visit is from late May, when the new green foliage is beautiful, through October, when the autumn colors are at their peak.

Access

Haneda Airport (HND)Travel timeabout 4 h 30 min
RouteTake Tokyo Monorail/Keikyu Line to central Tokyo → From Tokyo Sta., take Akita Shinkansen to Tazawako Sta. → Bus.
Narita Airport (NRT)Travel timeabout 5 h
RouteTake Narita Express to Tokyo Sta. → Transfer to Akita Shinkansen for Tazawako Sta. → Bus.
Tokyo StationTravel timeabout 4 h
RouteTake Akita Shinkansen Komachi to Tazawako Sta. (approx. 3h) → Take Ugo Kotsu bus for Tamagawa Onsen (approx. 80 min).
Shin-Osaka StationTravel timeabout 6 h 30 min
RouteTake Tokaido Shinkansen to Tokyo Sta. → Transfer to Akita Shinkansen for Tazawako Sta. → Bus.

Facilities with Analysis Reports

No facilities with registered analysis reports in this area yet.

Facilities Without Analysis Reports

Nearby Sightseeing & Local Cuisine

  • Obuke Fumarole: The impressive source area where 9,000 liters of hot spring water gush out per minute.
  • Tamagawa Onsen Nature Research Path: A walking trail through the geothermal area with rising steam.
  • Lake Tazawa: The deepest lake in Japan, known for its mystical, sapphire-blue water.
  • Hachimantai Aspite Line: A scenic driving route with beautiful views in every season, famous for autumn foliage and the "Snow Corridor" in spring.
  • Goshogake Onsen: A nearby hot spring famous for its natural mud baths.
  • Kiritanpo Nabe: A signature local dish of Akita, featuring grilled rice skewers in a warming chicken broth.
  • Inaniwa Udon: One of Japan's three famous types of udon noodles, characterized by its thin and smooth texture.
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References

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