Introducing Asahidake Onsen
This forested hot-springs village, at 1100m above sea level, has a few small inns at the base of Asahi-dake, Hokkaido's tallest peak. There are plenty of hiking options and healing onsen for afterwards.
Most onsen, even at the higher-end hotels, are open for day use to the general public. Prices range from ¥500 up to ¥1500.
Be prepared. There are no ATMs, shops or restaurants at Asahidake Onsen, so you'll need to have cash, and food sorted out if you are going camping or contemplating taking on the Grand Traverse. If you are staying, order meals at your accommodation house when you book.