Italian actor Stefano Fresi strides confidently through a protest scene as police detective Kostas Charitos in “Kostas,” a hit series on Italy’s Rai 1 network. Based on Greek author Petros Markaris’ beloved crime novels, “Kostas” introduces a Mediterranean detective icon to new audiences, bridging Greek and Italian cultures. Shot in iconic Athenian locations, the series has resonated widely, culminating in a second-season green light.