Although the recent economic problems have lowered the cost of traveling in Japan, the economy is bouncing back and in general, Japan is not a cheap place to travel. Unless you have friends or relatives to stay with, accommodation will be the most expensive cost with transportation following close behind. One way to keep costs down is by staying in hostels and cheap Japanese inns.
Some Japanese inns can be very reasonable and can be more interesting than staying in a hotel.
If you're planning on traveling a lot by train, it is definitely worthwhile to get a Japan Rail Pass before you arrive in Japan. If you have an international student card or Youth Hostel card you can save money on tickets and accommodation as well. Currency Exchange Japanese currency is the yen. Notes are available in denominations of Y1000, Y2000, Y5000 and Y10,000 with coins being divided in values of Y1, Y5, Y10, Y50, Y100 and Y500. Banks in Japan accept all major currencies, although it's a good idea to change Korean won and Taiwanese dollars into US dollars before you arrive.