Classification: Immortal human

Gender: Male

Age: 18 (1930) ; 90 (2002)

Height: 169 cm

Eye Color: Amber

Hair Color: Brown

One of the youngest members of the Martillo family and is a skilled fighter. He was orphaned at the age of ten and picked up by the head of the Martillo family after Firo attempts to rob him. In the Martillo family, he is tasked with monitoring casinos to prevent cheating, and later manages those casinos after becoming an executive member of the family.

When Maiza leaves the Martillo family in the 1970s, Firo is given the position as the family's bookkeeper until Maiza returns.