I wouldn't recommend sending a cash to anyone, 
its too easy for it to go missing. 

An alternative to an IMPO is simply to get the 
bank to write a check in a foreign currency, this 
is like a bank check but it is from the country 
of orrigin (ie Japan) so you will need a bank 
with an office in Japan (or affiliate there, 
which would just about be any bank). In this case 
you would end up with a Japanese Bank check, in 
Yen. Quite easy to organise and very safe to send 
(you can even query it like a normal check, and 
verify it is cashed only by the receiver).
(something like an IMPO but slightly different, 
guaranteed at the receivers end). 

The alternative is to organise a money transfer, 
again something any major bank does a lot of (the 
only places I have heard having problems with 
this are some South American / Affrican banks), 
ask to send it via SWIFT if you have any 
problems, you will simply need the receivers 
account and bank number (SWIFT Number, which the 
sending bank can look up anyway) again this is an 
international way of sending money which any bank 
will be able to do (they may not admit it but 
they all do it). 

Good luck