Firo is one of the heroes of Baccano!.
He is orphan since he was 9 and he lives in street, learning how to fight with knives and blades. There he meets Vino and they become friends.
He's found by the Martillo Family, and becomes its boss about 10 years later.
Since the begin of the series, he's the young boss of Camorra (Italian Mafia), an eccezional and rapid boy that fights his battle with intelligence and honour, and in privat life he's a good and loyal friend, that can sacrifice his life for the safety of his allies. Firo isn't just a classic hero that lives to fight, he's a funny and nice person that loves to stay with his friends, and with his lover.
In his first apparition he meets his friend Luck, that is in danger, and helps him to obtain reveange. Destiny wants that in a singolar circumstance he meets Ennis, the girl of his fate.
Firo is a very loyal person, and in the develop of the series he helps his friends (Isaac, Miria, Vino and the others), his lover (Ennis) and his mentor (Maiza-san!!), and at the end of the anime he becomes the boss of Camorra. When Ennis reveals him the secret to eat the immortals, Firo assumes Szilard Quates (Ennis' evil creator) and acquires his memories. At the end of the novel he get married with Ennis and lives with her the "rest" of life.