Nishiyama Onsen Shimonoyu Onsen Ryokan

The oldest bath at the bottom of Nishiyama Onsen in Oku-Aizu, once a full ryokan, now run as a simple day-use bath by an elderly woman who's often out tending her fields. The water is a chloride spring with the faint eggy sulfur characteristic of Nishiyama, served very hot straight from the source. It's an unpolished, completely local experience: call ahead, bring eggs if you want to make onsen tamago, and expect to share the tub with whoever else shows up.