Tokyo to Guangzhou to Hong Kong

Yes, your plan is definitely eligible for 144 hour visa free transit. Please, just try to use correct terminology because this is not 144 hour transit visa, but visa free transit, so there is no visa of any kind at all.

Please, keep in mind that you will have to buy y ferry ticket from Shenzhen (Shekou port) to Hong Kong through CKS - Chu Kong Passenger Transport Company website even before your departure toward Guangzhou. You will print it out and have that printout with you at hand, ready to be presented to relevant authorities. You should also have in mind that you will really have to take exactly that ferry you have bought your ticket for. One more detail. You flight to Guangzhou is not allowed to have any additional landing within mainland China of any kind. In other words, it has to be a nonstop flight from, for example US to Guangzhou.