72 hour visa using a return ticket to same country

I am Australian working in Japan (working visa)...I want to visit China for 72 hours (less actually) and would like to use the 72 hour free transit. I understand that you need to have a ticket to a 3rd country to be eligible. Some questions:
1) is it possible to use a return ticket to Japan as evidence for an onward ticket that would allow me to use the 72 hour free transit?
if not.....
2) if I go via a 3rd country ie South Korea airline where the flight lands outside of Japan (Seoul) before going on to Japan will that be adequate?
if not...
3) if I break my journey in South Korea would that make me eligible?
Sorry if the above is a bit confusing....