Shintamagawa Onsen

Shintamagawa Onsen in Akita is known as one of Japan’s best-known therapeutic hot springs, with highly acidic water and a healing atmosphere. Near Lake Tazawa in Semboku City, it’s sometimes called a “miracle spring” because of its reputed health benefits. The water is said to be Japan’s most acidic, at pH 1.05, and rich in hydrochloric acid. The spring has traditionally been used for toji, or therapeutic stays, and many visitors stay for longer periods in hopes of supporting their health and wellness. Parking space 11/12/25.

The highly acidic water here has a pH of 1.2 and can make your skin tingle. You can choose between the undiluted spring water and baths at lower strengths, including 1% and 30%. The baths are part of an inn scented with Akita cedar, and there’s also a private bath. Its large bath, made from acid-resistant Aomori cypress, has 14 bathing areas. The spring is unusual because it contains hydrochloric acid rather than sulfuric acid, and it also contains radium. It’s an easier hot spring resort to use than the main building of Tamagawa Onsen, which is popular with hot spring visitors, and it has specially designed rooms. Low pH means high acidity, and highly acidic springs can have strong sterilizing and keratin-dissolving effects. They can also be harsh on your skin, so rinse and moisturize after bathing.

In winter, heavy snow means you can only reach the onsen by bus. From tazawako station, the ride takes about 1 hour 20 minutes and costs 1,450 yen. The baths come in a range of types, including indoor baths with different pH levels, and you can feel the acidity on your skin as soon as you get in. The buffet is mainly Japanese food, with Akita specialties such as kiritanpo soup and local saké. Tamagawa onsen is among Japan’s most acidic hot springs, with a pH of 1. People believe it may have a broad range of health benefits.

The rooms were good, and the onsen was large and impressive. Because of the sulfur in the water, it’s recommended that you spend only a few minutes in the strongest baths. The place is used as a last resort by cancer patients. The food was the problem for us: it’s a buffet, and honestly, it was the worst food we ate in Tohoku.