Pardon the French, but ... WT* would you spend even 5 minutes in Narita.
If at least one of you is a female, I would suggest hitchhiking between Tokyo and Kyoto. When I used to hitch, I (well actually it was mostly my blond companion) would get invited for dinners and to spend the night at a lot of people's houses. Nice way to see the culture. If you're not that adventurous but still budget conscious, bus is the way to go.
If you're interested in contemporary culture, what's with Kyoto, the Matsuri, and Sumo. Hang out in Tokyo and go to a soccer match.
Love hotels can be a pretty cheap accommodation especially if you check in late.
At Narita, hang out in the parking lot or loading area in front of the terminal and ask foreigners getting into cars if they can give you a ride back to Tokyo (make sure to tell them you're a student on a really tight budget). If not take a local train (it's cheapest).
Last edited by 5khours; Mar 31, 2012 at 6:31 pm