buying JR pass in Japan?

Hello. I am in Japan for 2 months on a traveler's visa (temporary visitor) to visit a friend. I am staying in Nagano.
Another friend in Osaka suddenly said I should come visit, so I want to go from Nagano to Osaka and then back to Tokyo (to see another friend in Tokyo) by shinkansen.
It would be a big time and money saver if I could use the JR Japan Rail Pass since these trips are all close together and I meet all of the requirements except that I have to buy the pass outside of Japan.

Is there any possible way for me to get the discount pass (or a similar tourist discount for shinkansen trips between Tokyo and Osaka) from in Japan? I want to go on this trip in 9 days in the cheapest way possible (but by shinkansen due to time constraints).

So basically I need to go from Nagano �� Osaka (stay 2 days) �� Tokyo (stay 2 days) �� Nagano in the cheapest way possible.

Any suggestions? Do I really have to give up on the JR Pass just because there is nowhere here to buy it?

It would be a big time and money saver if I could use the JR Japan Rail Pass

No, it would not be a big time and money saver. Regular tickets would cost you only about 3000 yen more than a 7-day rail pass if you use the following route:

Nagano - (limited express) - Nagoya - (shinkansen) - Osaka - (shinkansen) - Tokyo - (shinkansen) - Nagano

You could further save money by taking a bus between Tokyo and Nagano instead of the shinkansen. By traveling by unreserved instead of reserved seats and by taking the one daily direct Shinano limited train all the way from Nagano to Osaka instead of taking the shinkansen between Nagoya and Osaka. Make also sure to buy a base fare ticket all the way from Osaka via Tokyo to Nagano instead two separate ones, assuming that you do both trips within the validity of ticket (I think it is 5 days).

I want to go on this trip in 9 days in the cheapest way possible (but by shinkansen due to time constraints).

Do you mean you will start the trip in 9 days or you will complete it within 9 days? In the latter case, note that regular tickets are even cheaper than a 14-day pass.

Additional tickets that will save you a few more yen on the Osaka-Tokyo route (e.g. Puratto Kodama Plan) are explained on the following page:
http://www.japan-guide.com/e/e4006.html

Of course, you could save the most by taking overnight buses.

Thank you for the reply!
I figured that the JR Pass would be cheaper because I need to use JR trains to get around for small travel while I am in Tokyo and Osaka.
And by ''in 9 days'', I mean I will start the trip 9 days from now so need to have my plans ready by then. :)

How long does the Shinano train take and how much does it cost? I am thinking of going to Osaka via night bus on the way there to save money, but past experience on the night bus was very unpleasant...

To get back to Tokyo, though, I will be in a hurry to get there as early as possible so I think Shinkansen is best. I read about the Hikari Hayatoku Kippu discounted shinkansen ticket on this site, but where can I buy it?
Thank you!

I figured that the JR Pass would be cheaper because I need to use JR trains to get around for small travel while I am in Tokyo and Osaka.

Samll JR train trips in Tokyo and Osaka typically add up to around 150 to 500 yen per day. They don't weight much for the overall calculation.

How long does the Shinano train take and how much does it cost?

You can look up schedules and fares on the following page. Enter "nagano" and "osaka":
http://www.jorudan.co.jp/english/norikae/

Shinano train run between Nagano and Nagoya, but one train per day goes as far as Osaka. You save about 1000 yen by using the direct Shinano train as opposed to taking the shinkansen between Nagoya and Osaka.

I read about the Hikari Hayatoku Kippu discounted shinkansen ticket on this site, but where can I buy it?

At JR railway stations.