LA- shanghai- hong kong- tokyo- shanghai- LA

I booked a roundtrip from LA to Shanghai.
I am traveling from LA, staying in Shanghai for 3 days, then traveling to hong kong for 3 days, then onto Tokyo for 4 days, then traveling back to shanghai to leave to LAX. when arriving back in Shanghai i am not staying to visit. i will simply catch another flight. would i need a visa or free transit entry would work? help