Bekkai-cho Furusato Koryu-kan

For anyone with their own car who likes driving around Hokkaido :) No detailed review, but there are lots of photos at the link. Price 510 yen. Usually associated with a ski resort nearby. I haven't been there in ages, but in the women's section there should be an outdoor hot pool in a beautiful garden, and a waterfall-style water massage (you sit outside on a rock and water from above massages your back). Things may have changed since then.