Onsen in Akita that has been popular with foreign tourists might be Nyuto Onsen.
But Tamagawa Onsen is the most popular hot spring in Japan for Onsen Freak and the sick persons need more remedy.
The hot spring is the most acid in Japan. If you take the onsen, you may feel prickly depending on sensitivity of skin.
Since the facility accept one-day bathing, you can try taking this onsen for your travel story.
Since the rocks around this Onsen contains radium(radioactive substance), many sick persons come here to take bedrock bathing.
Especially it has been said that bedrock bathing at the onsen is effective in the treatment of cancer.
Volcanic activity is observed on the trail and these rocks are warm. Many people lays down around the trail for own remedy.
The bus for this onsen runs from JR Tazawako(Lake Tozawa) station several times a day.
Tamagawa Onsen Official Website