Certainly, there are a million and one interesting places to go in this strange country, but if you decide to go and check one of them out, chances are that the equivalent population of a small European country will be there in their RVs, determined to "enjoy" it with you. Of course, the degree of overcrowding does depend on the season, so if you can avoid school holidays, public holidays, Golden Week (Late April/Early May), O-bon (Mid August), and just about any other time that you're free, you should have a pretty care-free time. Japan is a pretty sizable place, so I've split it up along some well known boundaries. Choose an area, and hit the road!!