When he Dou Dou sucked his blood otherwise he'll look like "dried duck at the market", he was referring to aged duck. A delicacy in china where the duck's bones have been removed and is curated by salt, hang to dry for aged flavour, very similar to prosciutto. Hope that helps.
So much have happened....the world is different from when it was 6 years ago...but this manga still slays... it is good to be alive in the middle of the pandemic (╥﹏╥)
We're back to square one y'all.
(っ˘╭╮˘)っ