Originally Posted by ROCAT

As others have said do not ask nor try to bend the rules it will not happen, but they will be nice about it. Also make sure your landing card or any other paperwork is filled out completely and correctly as immigration, customs, security and basically everyone else are sticklers about paperwork.

Despite speaking decent Japanese I still enter immigration in English so they know if anything comes up to use English. I had this happen once when I started the process in Japanese and it quickly went above my level which caused some confusion and slowed things down.