In the Hakkoda mountains, bathing since 1684 and Japan's first National Recuperation Onsen. A vast all-cypress mixed bath hall (about 260 m²) fed by four sources. Women-only hour 8–9 am daily; bathing garments sold on site.
The most polished of the seven Nyūtō inns, beside the Sendatsu stream and popular with women. Two sources — rusty 'gold' and clear 'silver' — in open-air baths above the rushing river. Day-use reception is short (10:30 am–2 pm), so come early.
At 1,800 m in Manza, four private sources feed eight open-air pools of milky, yellow and clear water — the famous 'Sekitei' rock-garden baths. Mixed bathing, but gowns or wrapped towels are required and there is a women-only pool. Day use 11 am–6 pm (last 5 pm), ¥1,700.
A wooden toji (therapeutic stay) inn over 200 years old on the Toyosawa River in the Hanamaki-Minami onsen area, once frequented by poet Kenji Miyazawa. Its signature is 'Osawa-no-yu', a mixed open-air bath jutting over the river, with women-only hours. Day bathing from 7 am; ¥700 covers three baths. Many linger for lunch and sake at the 'Yahagi' dining room. Free shuttle from Hanamaki Station.
A solitary forest inn five minutes by car from central Kurokawa, where the only sound is the headwaters of the Chikugo River. On roughly 10,000 m² of grounds sit the mixed open-air Moyai-no-yu and the women-only Shiki-no-yu, fed free-flowing from two private springs; the indoor bath has a faint blue tint. Day use covers the open-air baths only, 08:30–21:00, ¥600 for adults, and Kurokawa's 'nyūtō tegata' bath-hopping pass (¥1,500 for three baths) is accepted, so pairing it with inns in the village is the classic plan. There is a free rest corner after bathing. Closures are irregular — phone ahead.