Dinara
The hotel is a couple of km from Lake Yamanaka, with a view of Mt. Fuji. There is no higaeri, the onsen is on the first and second floors, and they switch them in the morning and evening: at first one of those two floors is for men and the other for women, then in the morning it is reversed. The first floor has a rotenburo, and the second does not, but instead they put in a sauna and a cold bath. Otherwise it is identical, with a large indoor bath in the center, and one end has a wall-mounted jacuzzi, so you can turn on the massage jets. The water is alkaline, clearly alkaline according to the documents, but perhaps because the source itself is not very hot and is heated, that seems to affect how the water feels, it is less soapy than you would expect at that pH.