Hi there,
8 Days is a nice period to explore Japan with! With the JR-Pass you can almost go anywhere!
Besides Kyoto, Nara and Fuji, I can also recommend a visit to Hiroshima for the peace museum and park. Also Takayama makes for a great trip if you would like to visit a more traditional village in Japan, also the train ride to Takayama is very beautiful.
Once you are in Kyoto, Nara makes for a great day trip and can be reached within an hour by train.
When you are back in Tokyo and would like to make an other day trip Nikko and Kamakura are very good options!
All places mentioned are covered by the JR-Pass, except for Fuji-san.
For instance you could do the following itinerary.
Day 1.) Arrival at Narita Airport + Tokyo
Day 2.) Tokyo
Day 3.) Day trip to Mount Fuji from
Day 4.) Kyoto
Day 5.) Kyoto + Nara
Day 6.) Travel to Hiroshima + Sightseeing.
Day 7.) Back to Tokyo + Souvenir shopping in Tokyo
Day 8.) Back to Narita Airport and flight home.
Hope this helps,
Daniel