I visited Hakuba this week for some snowboarding with my wife and a bunch of friends (we were a group of 9 in total staying in 3 different rooms).

We found K's House to be a great place to hang out when we were off the slopes. Toshi, Megumi and Manami were wonderful hosts, very welcoming and kept the place clean and tidy. They were always ready to help us arrange activities both on and off the slopes - driving us to the nearby onsen or recommending a soba noodle cooking course.

The rooms were small but functional, but it's the common room that really made the experience pleasant: plenty of room to sit, watch movies or play a game of backgammon.

I would happily stay at K's House Hakuba again.

Peaceful spot in the Japanese Alps. Toshi and his partner were super friendly and kind. They picked us up at the train station and took time to help us plan our activities. The rooms were clean, the common area was spacious and there is free internet access available.
The only drawbacks of this location is that, while in a quiet area it is a bit difficult to tour around without a car. There is a bus station nearby but buses come infrequently. There is the train station nearby but it is a painfully slow train (1h 45 minutes) to go the 60 km to Matsumoto. This made taking day trips a bit difficult. Also, there is only one restaurant within walking distance to the hostel but it is a good one with lots of character (gets a little tiresome after 3 or 4 nights though).
I would recommend this location for relaxing, biking and hiking.