William Camping in Japan is pretty relaxed. As long as you take care of fire (camping stove, not open fire) and trash, you can pretty much stake out a place and stay for free. (Be friendly.) Kumanichi remarks on a new campground at Ubayama (産山). I don’t recommend as I dislike established camping grounds, but the name “Ubayama” is interesting. Apparently, a couple of gods (well, probably one was a goddess) were getting it on and the result was the mountain.