K's was a very budget-friendly option for our family of four. It was a fun experience staying in the traditional Japanese room, but we did opt for an private bathroom. I didn't realise at the time of booking that the shower facilities were still shared, but this wasn't a problem (and even a bit quicker having 2 showers to use between us vs having one in our bathroom). Futons were fine to sleep on.
The view from the shared lounge area was gorgeous, and so were the surrounds. It is a little bit of a walk, and the hill is really steep, so catch the bus if you can! This was really the only downside of the property we thought - that it is a moderate way out of town, so make use of the property's free umbrella loan if you might be trekking back in the rain!!
We didn't use the onsen, unfortunately, so I can't add anything further on that. It was lovely to be able to grab a brewed coffee during the morning (0730-100, I think, but I don't know why you would still be inside at 1100 rather than getting out to experience the stunning Hakone area!).
