Hi Alfred,
Looks like a very nice trip you are planning. I have never been to Nozawa Onsen myself but it looks really nice.
As to your question, this one was somewhat hard to figure out but here we go:
Your trip would cost about the following if you just bought the tickets on the go:
Narita --> Tokyo ¥ 2,940 (With the Narita Express)
Tokyo --> Osaka ¥ 13,550
http://tinyurl.com/cdhd3b8
Osaka -->Hiroshima ¥ 9,750
http://tinyurl.com/bssgcth
Hiroshima --> Kyoto ¥ 10,590
http://tinyurl.com/cjpkuy2
Kyoto --> Nazawa Onsen ¥ 11,160
http://tinyurl.com/buu85z7
Nozawa Onsen --> Tokyo ¥ 8,900
http://tinyurl.com/bmsz46k
For a total cost of 56890 Yen. A 1-week pass costs 28,300 Saving you 28590 Yen and a 2-Week pass costs 45,100 Yen saving you 11790 Yen.
Besides this you can use the pass for local travel in Osaka and your days in Tokyo to save even more!
If you took the 7 Day pass you would have to shorten your trip somewhat in order to fit it all in.
So in your case I would really recommend the 2-week pass as it covers all of your big travelling. You could activate it on day 1 on Narita and tour Japan in comfort and without any hassle.
Here's some other tips you might find useful during your travel.
Since you are travelling from Kyoto to Nozawa Onsen there are 3 main train routes you can take.
(1) Kyoto-Kanazawa-Nozawa Onsen.
(2) Kyoto-Nagoya-Nagano-Nozawa Onsen.
(3) Kyoto-Tokyo-Nagono-Nozawa Onsen.
I would recommend that you take the 2nd route Kyoto-Nagoya-Nagano-Nozawa Onsen. This because the train ride between Nagoya and Nagano is very beautiful and besides that, this is slightly faster than the other two options.
If you plan your trip to Nozawa Onsen using Hyperdia.com make sure you use the station name TogariNozawaOnsen (and not just Nozawa as this will get you to some other place about 4 hours away from where you want to go).
Here's some more general information on how to travel to and around Nozawa Onsen:
http://www.nozawa.tv/english/access.html
As for your last days in Tokyo consider buying a 1 day unlimited metro pass.
They only cost 710 Yen and if you travel around a lot in Tokyo you can save at least double that!
You can buy these at any ticket machine.
Since you are in Tokyo during New Year's Eve, make sure that you listen to the Night Watch Bells that ring in all temples, welcoming the new year.
Also keep in mind that during the New Year period Tokyo for a great part shuts-down. So make sure to familiarise yourself with local conditions during New Year. Here's some good information on the topic.
http://www.japan-guide.com/e/e2276.html
Enjoy your trip in Japan, I must say that I am somewhat jealous of all the things you will do!
Kind regards,
Daniel
