Positive: The onsen is very beautiful. This is probably the biggest selling point for this hotel, it definitely was for us. Breakfast and dinner are also very nice, however it's the same every day. The staff was very friendly.
Negative: The hotel itself was partly renovated, but mostly the common areas. The rooms, especially the bathroom, is still quite old. The bathroom is extremly small and not cleaned very well. The hallway is tiled and the doors don't seem to be soundproofed, so starting at 7am in the morning you can hear the other guests going to breakfast very well. The rooms have a funny smell, I would say similar to hay or grass. Maybe it's coming from the Tatami mats, but it's quite strong. The rooms don't offer any Internet access, so either you need to have mobile data or go down to the lobby.
Conclusion: Would only recommend this hotel for one night, so you can enjoy the onsen. But aside from that, the price is not justified.