Originally Posted by hailstorm

The Karuizawa Prince Resort is a bit complex, with six separate entites: Prince Karuizawa East, Prince Karuizawa East Cottages, Prince Karuizawa West, Prince Karuizawa West Cottages, The Prince Karuizawa, and The Prince Karuizawa Villas.

The Prince Karuizawa and The Prince Karuizawa Villa guests are all allowed access to the Prince Karuizawa East onsen, but for the Cottage guests, onsen access is generally not included unless they are paying a special rate that specifically includes it. The Prince Karuizawa West opened its own separate onsen last year, but it is only included for guests staying in the Prince Karuizawa West Premium Wing of the hotel.

With all that said, it was always my understanding that everyone staying at the Prince Karuizawa East hotel building could use the onsen, so it's good to confirm that this remains the case for Hyatt booked guests as well.