Ryokan Ohnuma

Eight free-flowing baths of two baking-soda springs, four of them free private baths you just lock, a hillside garden bath and famous house natto — a modern tōji inn at old-fashioned prices, with stairs and shared toilets

Ohnuma has been a tōji (hot-spring cure) inn at Higashi-Naruko for over a century and is now run by the fifth-generation yumori, Ōnuma Shinji; it belongs to the Japan Association of Secluded Hot Spring Inns. Its draw is variety: two sodium bicarbonate ('baking soda') springs — its own pale, woody Ōnuma-no-yu and a clear, salty shared source — run through eight baths, all free-flowing with no added water or heating. There's a large mixed bath under a mural of celestial maidens, a women-only bath, four private baths (including a clothed hot-spring ondol and a one-person tub for guests who need help) that are free and need no booking, and the paid Mori-no-yu garden bath on the hill behind the inn. Japanese guests rate it 4.7 across 383 reviews on one major site, with service at 4.8, and 4.59 across 621 on another. They praise the staff (an elderly okami in kimono sees guests off), the skin-softening water, the moving between baths, and a breakfast of house-made natto from local soybeans and hot-spring tofu. The catches: 20 rooms in two old buildings with no lift, many rooms sharing toilets, thin walls in places, private baths on the fourth floor that may be taken when you've climbed there, bath temperatures that vary, and dinners too big for some. Two-meal stays run about ¥10,700–19,600 per person; self-catering tōji stays are cheaper still.