Carlo was a young Marleyan boy of short stature and slim build. He had a rounded nose and short blond hair parted down the middle. He wore round-rimmed glasses at all times as well as a standard Marleyan military uniform.
As a member of the Cart Titan's Panzer Unit, Carlo and three other of his comrades fought against the Mid-East Allied Forces at Fort Slava. Over a month later, Pieck reunites with her Panzer Unit while she and Porco Galliard are escorted away from the Liberio internment zone festival by a mysterious bearded soldier. Suspecting treachery, Pieck warns her Panzer Unit secretly to follow them from a distance.When Pieck and Galliard are captured by the soldier, Carlo and his comrades come to their rescue. Realizing they are under attack by the Attack Titan, Carlo and the others in the Panzer Unit quickly prepare the Cart Titan's artillery armor for battle.
Joining the fight alongside Galliard's Jaw Titan and Zeke Yeager's Beast Titan against the invading Survey Corps, Carlo assists Pieck by gunning down approaching soldiers, carefully conserving his ammunition as Pieck orders. However, when the Beast Titan is suddenly brought down by the Survey Corps' Ackerman, the Panzer Unit is caught off-guard by a wave of soldiers overhead. In the chaos, Sasha Blouse carefully snipes Carlo in the forehead from across the rooftop, distracting the others of the Panzer Unit shortly before the remaining three are annihilated in a barrage of Thunder Spears.