Do I need the JR pass?

In short, this depends on how often and how far will you commute within Japan..

If you are planning to cover only one or two cities then you would probably NOT need it. 

JR Pass is recommended if you plan to go around JAPAN covering multiple cities e.g. Tokyo to Osaka (and back) then Tokyo to Hiroshima then another city.  It does also cover Narita Express line from the Airport.

So all what you have to do is a proper calculation. If you are panning to only move from one city to another then buying individual Shinkasen tickets will be more affordable.