I'm living beside the lake Kussharo in the "Akan national park".
It's very quiet and beautiful scenery.
There are lots nature and hot spring facilities around here.
"Kotan Onsen" is One of the best outdoor hot spring by the lake. And its 3 min by walk from my house (Just across the road !).
you can see amazing sunset over the mountain from this hot spring !
I recommend you stay for few days.