For some very cheap cels, I've had them sent 
airmail. And every time I ask for airmail, I get 
warned by sellers that it is "a risk". I'm not 
sure exactly *how* risky it is, but I would 
hazard it has a risk level similar to sending 
things uninsured 1st class here - which I was 
once told is about one lost package per 70-80 
packages sent. (That might be right or wrong, but 
I was told that by one of those people who does 
nothing but Ebay things for a living.)

Your benefit is that *both* the US and Japanese 
postal systems are very good. I've never had 
*anything* get lost, cel-wise. . . But then, I 
don't use airmail often either.

Many Sharp Smiles,
--Drac