Kawashima Inn

Kawashima Inn sits in Toyotomi Onsen, a small hot-spring town in Hokkaido known as Japan's northernmost. The spring itself was found by accident over a century ago, when workers drilling for oil struck hot water instead, and the water still carries a trace of that origin: it runs faintly yellow and cloudy, has a light oil sheen and a mild petroleum smell, and is known locally for its effect on skin conditions. The two indoor baths, each with its own attached rotenburo, are kept at different temperatures including a properly cold plunge, and the water is kept flowing fresh from the source. Which bath is for men and which for women swaps every day. A reservation-only private open-air bath is also available; the inn's two deluxe rooms open straight onto it, though it's shared rather than exclusive to the room. Rebuilt in 2016, the inn has a deliberately plain, cabin-like feel: pale wood, natural materials throughout, and a double-height lounge with a wood stove where guests gather. It has 15 rooms in all, and day visitors can use the baths in the afternoon.