flight to Okinawa during a China stay

Hi, I have a 1 entry visa to china and currently traveling through china. I will spend a few weeks in Shanghai where I'd like to take a plane to Okinawa. my return ticket from Shanghai to France is already booked, so can I fly to Okinawa, return to Shanghai within 72 hours of my flight back to France and get a 72 hour permit? in the worst case, can I return to Shanghai the day of my departure to france and register the ticket within the transit area?

thanks