Single or double entry visa required?

Hello,

I am Australian living in Japan on a working visa. I will travel for 7 days on a Royal Caribbean cruise ship leaving from Baoshan, Shanghai on July 7, 2012 and returning to Baoshan on July 14.
Will I need a single or double entry visa for the following itinerary?
- fly Tokyo to Shanghai July 6
- depart shanghai on cruise ship on July 7 to go to Japan and South Korea
- return to Baoshan on July 14
- fly Shanghai to Tokyo on July 14

I am asking because the cruise contains international travel.

Thank you for your help.