72 Hour Transit Visa: Tokyo to Shanghai to US (via tokyo)

Hello,

We will be traveling through Shanghai to go to the United States. We will depart from Tokyo and arrive in Shanghai, stay for 2 days and then depart Shanghai for the US, however our US flight has a connection in Tokyo. Will we qualify for the 72 hour transit visa? Do we apply for this at the airport?

We are US citizens, with US Passports.

Many Thanks!