Bruno is a central character introduced during the World Racing Grand Prix arc of the anime, known for his ties to the future and his role as a mentor to the protagonist, Yusei Fudo. Initially appearing as a friendly, amnesiac mechanic with a knack for machines, his background is far more complex. He originates from a desolate, apocalyptic future as a human named Johnny, a professional Turbo Duelist who relied on Synchro Summoning. After the world was ravaged by the Meklord Emperors, he was saved by a being named Z-one and eventually died, only to be recreated as an android. This android was sent back in time under the code name Antinomy with a specific mission: to ensure Yusei Fudo grows strong enough to save the future.

In the present timeline, Bruno suffers from amnesia and is discovered unconscious on a shore in the Satellite district. Despite his memory loss, he is exceptionally intelligent and possesses mechanical skills that rival even Yusei's. He quickly becomes the super mechanic for Team 5D's, working on their Duel Runners with an almost obsessive passion, often inspecting any machine he finds impressive without asking permission. His personality in this state is gentle, sociable, and pacifistic; he frequently states his opposition to violence, especially when confronted by the hot-tempered Jack Atlas. He is deeply curious about his forgotten past, believing everyone has the right to know the truth about themselves.

As the story progresses, Bruno's role shifts from a supportive crew member to a crucial combatant. He harbors a secret identity as a mysterious Turbo Duelist known as Dark Glass or Vizor, who challenges Yusei to teach him the advanced technique of Accel Synchro. Eventually, he recalls his true purpose as Antinomy, an ally of Z-one. His mission is to push Yusei beyond his limits, but he continues living with the team because he values his friendship with them. This conflict culminates in the Ark Cradle arc, where he reveals his identity and duels Yusei. Though he claims to be an enemy, his defeat reveals his true intention: to teach Yusei Delta Accel Synchro so that Yusei might save both the world and Z-one.

Bruno stands out due to his remarkable abilities. As an android, he has an active state where his eyes glow red, granting him superhuman strength, agility, and reflexes. He can materialize his yellow Duel Runner, the Delta Eagle, through a signal emitted from his eyes. He is also a left-handed duelist, wearing his Deck on his right arm. As Antinomy, he pilots a deck focused on the Tech Genus archetype and is a master of high-speed summoning techniques, including Accel Synchro and the ultimate Delta Accel Synchro, which he achieves through states called Clear Mind and Top Clear Mind. While he never becomes a Signer like his teammates, his technical expertise and combat prowess make him invaluable to Team 5D's. His ultimate act is sacrificing himself to ensure Yusei can return from the collapsing Ark Cradle, solidifying his legacy as a true friend and guardian.