Nozawa Onsen is located in northern Nagano Prefecture, host of the 1998 Winter Olympic Games. With 30 distinct hot springs and 13 public onsen, or soto-yu, Nozawa Onsen has been renowned for its hot springs since the Edo Period (1603–1868).

The soto-yu, cared for by a villagers' association called yu-nakama ("hot water friends"), are open from 6 a.m. to 11 p.m., and are free to use. The water runs very hot, though some—including O-yu, the best-known soto-yu—have cold-water taps to help bring the temperature down. And one, Kumanotearaiyu, hovers at a "cool," 41 to 42 degrees Celsius.