Hachimantai Heights

Hachimantai Heights draws its baths straight from the Hachimantai onsen, a sulfur spring known locally as Magma no Yu (マグマの湯). The indoor baths and the reservable private hinoki bath (barrier-free, bookable for a family at a time) all run on that source, and reviewers describe the water as smooth and faintly slick on the skin. Outside are two rotenburo, one set with rock and one built from hinoki, fed by a mix of the same spring and well water; the men's and women's sides swap daily, and Mount Iwate is in view from both. There's a sauna inside the main bath on each side, a footbath filled with onsen water out in the forest, and a ganbanyoku (岩盤浴) room that uses radioactive Hokuto stone (北投石). The hotel sits in a stretch of forest on the Hachimantai plateau, with an easygoing restaurant and a garden that looks out at the mountains. Several room types have their own hinoki tub, indoor or open-air, but those run on groundwater off Mount Iwate rather than onsen water. The one exception is the Himegami annex (別館姫神), a suite with history: Emperor Showa once stayed there, and it still keeps furnishings from that time. Its private hinoki bath is the only one in a guest room that's genuinely onsen water, filled 100 percent kakenagashi (掛け流し) straight from the source.