Motoyu Shinsenkan Nikori Hot Spring

Tucked into a mountain caldera a few kilometers from the Funka Bay coast, Motoyu Shinsenkan Nikori no Yu sits on the original spring site that locals say is one of the oldest in Hokkaido. The bath itself is completely unmanned: buy a ticket from the vending machine, drop it in the box, and you're in. Inside there are three indoor baths at different temperatures and one open-air bath, all fed with natural spring water that is undiluted and unheated. The water runs pale yellowish and feels faintly smooth on the skin, with a slight saltiness. The Showa-era atmosphere and the mostly local crowd give it a genuinely well-worn feel that keeps regulars coming back.