Ryokan in Nagato Yumoto Onsen

The three reviewed inns sit along the Otozure river in Nagato-Yumoto, an onsen town being remade since 2016 around a walkable riverside. All three use an alkaline simple spring, and none sends free-flowing source water into its shared baths unaltered: the big baths are recirculated or partly heated, and the purest water is in rooms with their own bath.

Otani Sanso (classic) is a large, polished 98-room resort with strong service and cleanliness scores and a much-praised breakfast bread; book one of its 21 suites if you want free-flowing onsen, and avoid the cheapest twins facing the car park. Its sister Bettei Otozure (premium) has just 18 rooms, each with its own free-flowing open-air bath, and a light local kaiseki served course by course; it takes no children under 13, and the cheapest maisonettes have steep stairs. KAI Nagato (classic) is the newest, opened in 2020 as part of the town's makeover: a 40-room Hoshino Resorts inn full of Yamaguchi crafts with free sake after the bath and a winter fugu upgrade, but its single large bath is small, the cheapest rooms have showers only, and 2026 guests found the meals uneven.