Can i buy a cheap chip to use internet in my iphone arriving to Japan?

Question:

I want to use my iphone to translate things and use the maps, could I buy a prepaid chip at the airport in Japan?

Answer:

I don't know if you can get the SIM card at the airport (You can get a prepaid mobile phone there, though.)
but in Japan you can buy a SIM card at "b-mobile".
http://www.j-com.co.jp/en/index.html
http://www.bmobile.ne.jp/lineup.html

If you get a "talking SIM", you can make a phone call, and if you get "b-micro SIM", you can only access the Internet (and it's cheaper).

Both types of SIM card, standard SIM and micro SIM are available.

The problem is whether your iPhone is SIM-free or not.
If you got one in the US, probably your iPhone is SIM-locked, which means it doesn't accept other SIM card, whether abroad or in the US.