a fully refundable ticket from jp?

I will be entering Japan without a work permit (I am american, so I get the 90 days visa wavier) since I am planning to obtain it as my company told me to do. However, I am a little concern that the customs or the airline will bug me for the date of outbound flight.

I believe the best thing I can do in this case would be to purchase a fully refundable ticket and show it to them, then cancel it afterward.

Do you guys have any suggestion where I can do that?

thanks in advance

James

Or buy a discount (reasonably priced) roundtrip ticket that get you back to the US within 90 days, and just not use the return. Or buy an open roundtrip ticket (you can change the return date - up to six months, or one year or so I think). This will be a bit more expensive, but I assume that your company will be paying for your trips?