Ofc he's not gonna shake your poop hand...
Unless they wipe their ass with magic they are probably using the left hand, the one they don't eat with.
But who knows, maybe most people in that world is left-handed.
What is the actual reason manga/manhwa/manhua artists draw people shake with their left hand?
Is it just simply because they can look at their left hand while drawing, or is it some asian culture thing?