Hotel Sunvalley Izunagaoka

The shared bathhouse is the centerpiece here, a tall cypress-lined hall with indoor tubs and a sauna, and the two rooms (Ichi-no-yu and Ni-no-yu) swap between men and women daily, so it is worth checking the schedule before you go. Beyond it are private baths with an open-air tub, each in its own small room, which can be reserved for an extra fee. Some room types in the main building come with their own private open-air onsen bath as well. It is a sizable hotel complex spread across a few buildings, with a buffet restaurant and gardens, and the water itself is genuine hot-spring water piped straight to the baths rather than through any dilution or reuse system.