do we need it?

HI Hiyas,

Yes, I recommend using a 7 day JR pass for your trip.

Just visiting Osaka - Hiroshima - Kyoto - Tokyo will more than pay for the JR Pass. You'll be making great savings and the JR Pass will cover travel between all the above cities.

Fuji may require a bit of additional travel, depending on where you plan to visit. For some ideas, have a look at this page.

Hope this helps,
Daniel