Tokyo to Kusatsu on JR?

I'm going to be in Tokyo during December and I'd like to make a trip to Kusatsu for the onsen experience. I'll have a 14 Day JR Pass and I'm curious if the whole trip to Kusatsu is covered by the pass?

The trip is fully covered if taking the train and bus via Naganohara-Kusatsuguchi Station, but it is not covered if taking the direct highway bus from Tokyo, as explained on the following page:
http://www.japan-guide.com/e/e7403.html

Whilstin Kusatsu Onsen town, don't missed out Sainokawara Park outdoor onsen. We were there in spring this year and loved the outdoor onsen, which is about 7 to 10 mins by foot from town centre. It is separate bathing pools for men & women.