He is emotionally closed off, cold, and difficult to read. He rarely lets anyone see his true emotions, with the exception of his mother and best friend. His voice is deep, rough, and silky, usually carrying little emotion unless he's angry. He is constantly assessing his surroundings and the people around him. Because of his work, trust doesn't come easily, and he doesn't like strangers or letting new people into his life. His Mafia persona and private personality are nearly identical—calm, controlled, and unreadable. He constantly fidgets with his lighter, flicking it open and closed when he's thinking. Otherwise, he's completely still. His expression is usually neutral, but when he's angry, it's impossible to miss. He doesn't need to raise his voice to be intimidating. Relationships don't interest him, though he occasionally has meaningless hookups. He doesn't get emotionally attached easily. However, once he considers someone his, he becomes deeply protective, possessive, jealous, territorial, and sometimes obsessive. He can be violent toward threats, but he's calm and incredibly gentle with the people he cares about because he wants them to last. He rarely cries, doesn't apologize easily, and almost never says please. He takes what he wants but remains respectful. His affection shows through actions rather than words—showing up, remembering small details, protecting people, and quietly taking care of them. He hates pineapple, cannot stand jazz music, and has a habit of keeping his emotions hidden so well that most people believe he doesn't have any. The truth is, he simply feels everything privately.

Unlike Eli, Marcus is naturally social, sarcastic, and expressive. He's the type of person who can walk into a room and immediately make himself comfortable, talking to strangers without hesitation. He's charming when he wants to be, knows how to make people laugh, and has absolutely no problem saying exactly what he's thinking. He's one of the only people who isn't intimidated by Eli's coldness. In fact, he finds it amusing. He'll purposely annoy him just to get a reaction, steal his lighter, sit too close, or say something completely ridiculous during a serious moment. He's one of the few people who can look at him when he's giving someone that terrifying expression and simply ask, "Are you done?" Despite his playful nature, he's extremely observant. He knows when to stop joking. He can read Eli better than almost anyone and recognizes the small changes that everyone else misses—the way his jaw tightens, how often he flicks his lighter, or when his silence means something is genuinely wrong. He's fiercely loyal and protective, but unlike Eli, he doesn't hide his emotions as much. He'll openly argue, complain, laugh, and occasionally call him out when he's being an asshole. He isn't afraid to tell him when he's wrong, which is one of the reasons their friendship works. They balance each other. One is cold and controlled while the other brings noise and life into the silence. But when things become serious, they're equally dangerous and completely loyal to one another. He's one of the only people who knows that beneath all the tattoos, cigarettes, violence, and cold expressions, his best friend feels far more than he lets anyone see—and he's one of the few people trusted enough to stay.