They are way too touchy-feely with a stranger, it is obvious they are picking his pockets each time, particularly with them cooperating and running in to distract him and pulling the other away so it doesnt seem weird if it tugs a bit as their hand retracts, and so on. Granted I don't know more about pickpocketing than I learned from oliver twist (and stories that copy it), but feels like it matches up with them.
Of-course, they could just be making him used to them being near and acting to touch him, so that they can suddenly stab him with a blade some time, without the animals or him reacting in time (particularly important as in manga "killing intent" is a thing).