We stayed one night in a separated room with private open-air bath (non-smoking) for an anniversary trip, and it was an absolute pleasure. The room itself was two floors, spacious, scrupulously clean, with a bedroom area above and a lounge area below. The lounge was equipped with a large pit-style kotatsu that we enjoyed between baths.
The room's private hot spring bath was in a little area behind the room, surrounded by little trees and enclosed by wooden walls. It was very large compared to other private room baths we've had, and easily fit both of us in full recline with plenty of room to spare. The continuously circulated hot spring water itself was cooled to a very pleasant 42 degrees C or so. We took around seven or eight baths. The only small negative point of the bath was that it had a slight chlorine note that covered up the usual sulphur, but the onsen had their required certificate that verified the water as genuinely volcanic and gave its mineral breakdown, so it wasn't like they were covering anything up.
The included six-course dinner and breakfast were delicious, though not the full, elaborate kaiseki style that some other places do (for a much higher price point). In consideration of the ongoing COVID-19 pandemic, all ordering was done via a smartphone website that opened when we scanned a QR code at our table. The website offered both an English and Japanese interface.
English spoken by the front desk was adequate.
Overall, an excellent place!