Dal Shabet

--What makes you think I should know every single one of my sister's friends? But that's not the point. Let's say she really does have an acquaintance here. But judging by the tracks, Ilaria, Agnet, and Maria were walking together. And there was a fourth person with them. Is he their mutual friend? But that can't be. So who is he? And what does he want? I do have a theory, but...