Taisenkaku

This ryokan sits on the Chikugo river at Harazuru onsen, a hot-spring town with more than a century of history along the same stretch of river. The two main baths swap between men and women each day: one is a jungle-themed hall with half a dozen small tubs, a water slide, a sauna and a jet bath; the other pairs a semi-open-air rock bath named for a local kappa legend with a plainer indoor bath next door, also with its own sauna. Two small private open-air baths further back in the garden, one facing a waterfall, can be booked by the hour, including by day-use guests. The spring water is a blend of alkaline and sulfur water with a faint sulfur smell, said locally to leave skin smooth. It's set up for families and multi-generation trips, with kids' yukata in three sizes, table tennis and karaoke rooms, and a summer outdoor pool, plus three annex rooms with their own onsen bath for couples wanting more privacy.