Currently at this property. Hotel is booked out so no upgrades available, latest check out was 1pm. They gave a small appetiser platter and 2 cans of beer to make up for the lack of upgrade, so that was nice.
One very annoying thing is that there is no AC in the rooms, at least in Spring (end March 2024). The temperature is centrally controlled so it is set to heating by default. The Japanese (which is their main clientele) like it warmer, so that was a problem for me and those who prefer it colder. The only option was to open the window and they brought me a fan as well. Also, if you are a light sleeper and can't sleep with noise, DO NOT book the rooms with hot springs. The water cannot be turned off and it can be annoying at night for light sleepers.
Air Conditioning is mentioned as a room feature on Marriott's website, so that's a bit deceptive.
I guess people who are kept awake by the flown of onsen water should probably never go for an over water villa in a beach resort, or ocean front a Pacific or Atlantic coast line.
It is indeed a constant sound in rooms with onsen.