We had what must be the smallest configuration of 'apartment' at Yama Shizen (East), more akin to a twin room in a hotel, a small sink and service area with a toaster, microwave and bar fridge. There was however no stove-top. I could not in all honesty acknowledge the accommodation as an 'apartment': a bed-sit at best.
I know the other units are more apartment-like but I guess we weren't on the higher rate. However, as much as our accommodation was like a hotel-room there are some important differences mostly around the services (or lack thereof).
Bed-linen was changed once during our 7 night stay, trash emptied every other day and tea, coffee and milk provided but once (on arrival) and never thereafter replenished. The eco-room service is 'economical' for the hotel, not 'ecological' as you might think: trash is removed, towels are changed but there is no cleaning or tidying. There are no facilities on-site, no gym. no spa, no pool. There is an onsen up the street.
A few other negatives. There was a bean bag, with no beans in it, the foyer smelt like trash and is mostly filled with left luggage, the TV is too small. The adjacent larger apartment was unoccupied but no one offered to upgrade us, I would have been happy to pay extra.
A few positives: the pick-up service on arrival is excellent, the staff are very friendly, there is an Apple TV, a 90's stereo, the beds are very comfortable, the shower is excellent, there are facilities to wash clothes, it is toasty warm.