Hi there,
Lets take a look at your ticket costs for the last 14 days of your journey to get a handle on if it'll be cheaper to use a 14 day JR Pass (¥45,100):
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Tokyo > Hiroshima: ¥17850, (295mins, 894km)
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Hiroshima > Kyoto: ¥10990, (126mins, 380km)
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Kyoto > Nara: ¥690, (44mins, 41km)
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Nara > Osaka: ¥780, (55mins, 48km)
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Osaka > Narita airport terminal 1: ¥16250, (272mins, 635km)
JR ticket cost: ¥46560 for 5 legs
- 14 day rail pass (¥45,100) saving: ¥1460
As you can see, there is a small saving to be made with the 14 day pass over standard tickets. As you'll make some savings, and have the added flexibility to use the JR Pass on JR lines in Tokyo and other journey's as needed throughout the 14 day period I can certainly recommend the 14 day pass option.
For the first day into Narita, I recommend the [Narita Express + Suica prepaid metro card package] purchased at Narita on arrival. This will get you into town on the Narita Express and give you ¥1500 of free metro or JR travel, allowing you to use Metro for the first week you are in the city at a discount. You may also want to look into the 1 or 2 day discounted metro passes available at Narita.
Hope this helps!