[Sangetsu]

Go to Japan Railways site and see what's available. Most unlimited use passes must be purchased outside Japan. Once you get here you'll have to pay the same rate everyone else does.

Odds are you'll spend less than 1000 yen per day on train fair, so if a one-week pass costs 10,000 yen or more, you're better off just paying the normal ticket price.

On second thought, I noticed you'll be traveling between Tokyo and Osaka. Tourist can get a JR train pass which also included unlimited use of the Shinkansen (bullet train). Otherwise a reserved seat on the train from Osaka to Tokyo will cost around 17,000 yen each way. A pass would be a good deal for you. The Shinkansen is the best way to get from Osaka to Tokyo, otherwise you would have to endure an overnight bus ride. The Shinkansen can make the trip in only 3 hours or so.