As expected from the ryokan around this area, the spring water they use in the onsen feels wonderful on your skin. The onsen has indoor area, and an outdoor bath which opens to the great sea view. Even if you're not a fan of the idea of going naked in a public bath, I'd still recommend that you try it here. The common bath opens all night until morning. I went there late at night when there was not a soul, and it felt so unreal to have such a big bath all to myself. You can't see the view when it's dark out though.
If you're travelling there by train, you should inform the hotel staff the time of your arrival at the Noboribetsu station, so that they'll arrange the shuttle service for you. I put my special request on this website well after the booking, about two weeks before travelling. They sent me an email to confirm in less than a day. On the day of my arrival there was heavy rain so I was really glad that I didn't have to walk. Not to mention the place was further away from the station than I thought too.
There isn't much to say about the rooms. If you have an idea about Japanese-style ryokan where you sleep in the futon on the floor, you know what to expect. The room is very clean, no bath or shower en-suite, there's modern toilet, and a big window overlooking a nice view outside.
Come to think of it, I'd like to go back and stay for a couple more nights. Maybe someday.