Ichinobo

Ichinobo is a large resort ryokan above the Hirose river at Sakunami Onsen, on the edge of Sendai. The main outdoor bath is a row of four pools at different temperatures right along the water, plus a smaller, quieter nature bath elsewhere on the grounds that tends to run cooler. Bathing alternates between men and women by time slot rather than mixed. There's also a big indoor bath and an herbal mist sauna scented with mugwort, though no dry sauna or cold plunge. The spring is the resort's own, and the water itself is mild and clear rather than strongly mineral. Some of the higher room categories add a private open-air bath on the terrace. The stay runs all-inclusive, meals and drinks folded into the room rate, and it's an overnight-only retreat with no day-use bathing.