A route around Japan for my trip?

I'm going to Japan for about 6 weeks, it can be extended, and I wanted to pick some locations that pretty much make a loop. I'm planning on starting at Narita and then going, in this order, to Tokyo, Nagoya, Kyoto, and then Osaka. I want another 1 or 2 locations that are on the way back to Narita so I don't have to travel for hours to get to the airport. Any good ideas? I really need some, thanks!