Just got back from Onuma, which was a lot of fun. First there was the Onuma Park, which unfortunately the group of people that I was with was not able to explore, since our lunch took so long to get.
But afterwards at the hotel we had a lot of fun. There was karaoke, sport slide, and onsen. Although it was quite embarrassing in the beginning, the hot water made it worthwhile. Definitely thinking of going to one again.