Hi there,
An easy to travel itinerary would be something like Tokyo - Kyoto - Osaka and make a day visit to Nara or Himeji.
Tokyo is great for shopping experiencing the modern Japan and offers tons to keep you busy. Kyoto makes for a nice switch to more traditional Japan with Temples, gardens and the Geisha culture. Then you can spend a day or two in Osaka to visit Universal and do some shopping before returning home. If you want to see a bit more of Japan make a day trip to Nara and see the big Buddha or to Himeji to see the castle.
If you are looking for a bit of a romantic scene, consider a visit to Koya-san and stay the night at one of the local temples, or head to Kinosaki-Onsen and stay at a traditional Japanese Inn (Ryokan).
By traveling one way Tokyo - Osaka, you'll most likely may not require a JRPass. However it may be worth your consideration if you would like to travel more south as well to visit Hiroshima or even Kyushu.
Hope this helps,
Daniel