144 Hours Visa-free in Guangzhou

Hi, we have a flight from US to Hong Kong, planning to take a Railway train from HK to Guangzhou, staying for up to 6 days for the Canton Fair, and also then to catch our next flight out to Tokyo (Narita) and back to US.
So, flight US->HK; train HK->GZ to catch the flight GZ->JP; and back home JP->US;
Would we be eligible for 144 hours Visa-free in GZ with this flight pattern/stopover? Thank you.