Man X (男X Otoko X) is a tertiary ally featured in the fifth part of JoJo's Bizarre Adventure, Vento Aureo. He is a gangster that Giorno Giovanna thinks of as a hero. After his life is saved by a young Giorno, the man treats Giorno with respect and ensures nobody would mistreat him.
Man X is an adult Italian man with an athletic build. He has long wavy dark hair kept at shoulder-length. His irises are never shown as his eyes are depicted as shadows instead. He typically wears a fedora along with a suit.
Man X is a mysterious individual. Giorno feels that Man X is just like him, appearing lonely and melancholic. Despite being a gangster, the man has a strong sense of justice and repays his debts. Although he would keep his distance and only watch Giorno from afar, Man X treats Giorno with respect, ultimately teaching Giorno the importance of trusting people from their silent interactions. He acts somewhat cruelly by not speaking to Giorno, trying to ensure that Giorno doesn't get involved with gangs.
The anime expands on his personality by adding more to his flashback. He seems to be respected in his community, as the owner of an ice cream shop says the man always takes care of him and gives Giorno a free ice cream. He has no qualms about killing a boy's father because the man was selling drugs on his turf to even women and children. Giorno inherits how the man feels about drugs and eventually gains the dream of ridding Italy from gangsters who sell drugs to children.
Man X is first shown hiding in an alley from a group of suspicious-looking men, severely injured with gunshot wounds. When Giorno Giovanna was walking home from school as a child, he finds the man lying on the ground. Soon after that, the group of men ask Giorno if he saw the man running away. Giorno saves the man by lying and unconsciously using his Stand, making grass grow long enough to hide the man's body. Giorno believed the man looked lonely and melancholic, just like he did. The man turns out to be a gangster and promises to repay the child for saving his life.
Soon after that, Giorno's Stepfather stops hitting him and the kids that bullied him at school start being surprisingly friendly, such as giving up their seats to him in crowded movie theaters. The man only quietly watches over Giorno from afar but Giorno learns the importance of trusting people from this complete stranger.
The anime adds a scene of Man X shooting someone in an alley and then speaking with his partner afterwards. Giorno sees him and runs up to him, but the man silently walks away. Just then, a boy runs up to them and points a gun at the man, shouting that the gangster killed his father. Man X explains that he killed the boy's father because he was scum who was selling drugs to women and children on his turf. The boy attempts to shoot him but fails, and breaks down crying thinking that the gangster is also scum. Man X then walks away, inspiring Giorno.
- “Your dad was scum. He broke the rules of my turf by selling drugs. He even sold them to women and children. That's why I killed him.”
- The gangster is named Man X in the anime credits and Stardust Shooters. He is referred to as Mr. X in the English dub.