I'm planning to travel to Shanghai for less than 72 hours, just for tourism.

However, there is no third country I plan to transit to. Is a third country to transit to essential for me to qualify for the 72 hour free visa? For example, I'm leaving Japan on Saturday night and returning to Japan on Monday night (not a Japanese national, I'm American and just live there for the time being). Thanks for the help! I can't seem to find a clear answer anywhere...