Martino was an old man who had white hair and a neatly trimmed beard. His eyes were wide and alight with mischief. He had a large nose and mouth, and he had a long scar running down the right side of his face from hairline to chin. He appeared to be in his forties or fifties, an improbable age for a mercenary, with many lines across his face. Overall, he was not too dissimilar to Gambino in appearance, but was vastly different in personality.
Martino was a jovial man, and was cunning and clever. Not much appeared to bother him, as Guts' incredibly hostile attitude towards him when they first met did not seem to bother him, nor did the implication that he was a predator.
Martino, though much kinder than the likes of Gambino, was a hypocrite: though he reprimanded the guards for beating Guts, he later convinced Guts to make a break for freedom, getting him severely wounded and recaptured in order to secure his own escape. He was not above routinely placing Guts in danger or using him as bait even when Guts joined his mercenary group for a short time, though this seemed to be borne out of a lack of caring rather than outright malice. Though he clearly placed a much higher value on his own wellbeing than on Guts', he was happy to see the boy come out of things alive and would always repay a debt.
Guts first met Martino when the latter displayed some appreciation for his slyness alongside concern for his wounds. He taught Guts what was done with captured mercenaries like them: they were used as labor to build the kingdom's buildings and monuments. When Guts fell over, Martino berated the guards for beating a kid and tried to help them up. Though violently repelled when he first attempted to touch Guts, he was able to convince him to lean on his shoulder, given his injuries, and was unbothered when Guts implied him to be a predator. He later gave Guts a stolen key and used it to unlock his shackles, convincing him to run for freedom. However, Guts' wounds prevented him from making it far, and he was shot in the back by several arrows and recaptured. Martino, however, easily escaped from his own manacles and salutes Guts as he makes his own, successful escape.
Guts would later join Martino's band of mercenaries, where he was routinely humiliated and injured due to Martino using him and other trusting men as decoys or bait. When Guts furiously brought this up after a battle, angrily remembering how Gambino would do the same thing, Martino laughed it off and told Guts to use the experience as fatherly advice, that he should get by on his own brains and skill and trust no one else, even his own father.
After Guts escaped the pre-arranged execution match with a viscount's son alive thanks to Chitch, Martino attacked the courtyard with some men, smiling when he saw Guts mostly unhurt despite an arrow nearly pinning Guts to the viscount's son's and killing him. Guts would leave Martino's band after placing a flower in a field, likely pushed past his limit with near-death experiences at Martino's hands. He would go on to meet Griffith later that year.
- It is implied that Martino knew of the Band of the Hawk: when he claimed that if Guts were to find an unnamed person or group of people, they might give meaning to his life, with the image of a white hawk being shown in the sky.