Genshichi Roten no yu Zao Onsen

Just went here. Awesome for 600 yen. The indoor bath is wooden, hot, but perfect after trudging through snow, plus the wall by the water source is also made of wood with gaps, which makes it more comfortable to sit there. The same water flows from the bath into the rotenburo. The rotenburo is stone, the water is cooler, so you can hang out there for a long time and zone out watching the snowdrifts. The main plus - Chinese group tours apparently don't know about it.