Breo was a street Duelist prior to joining Team Unicorn (known as the Baron of the Backroads in the dub). His personality was much more self-centered and boastful during this time.
He apparently had an impressive winning streak and believed himself to be the best. One day, when he arrived at where he usually practiced, he found Andre and Jean tuning up a Duel Runner.
When they refused to leave, he challenged them to a Duel. After losing to Jean, he is invited to form a team with Andre and Jean. During all the tournaments that follow, he's never had to Duel until the WRGP, since Andre has been able to handle it all on his own.
Breo is at the opening ceremonies for the WRGP along with his teammates. Crow Hogan takes Yusei Fudo over to speak to Breo and his team mates, but when Yusei wonders off as he was wondering about how to tackle the "Meklord Emperors", Crow apologises to the team then runs off to which shocks Breo.
A few days before the start of the World Racing Grand Prix, Breo is practicing with the rest of Team Unicorn when Crow crashes into him. However, this is a part of Jean's elaborate plan to see Yusei's Deck and his strategies. Breo watches Andre's Duel with Yusei afterwards, all the while formulating a strategy that can counter Yusei along with Jean, complimenting Yusei's tactics in the process.
Breo is the "Second Wheeler" or second Duelist, on Team Unicorn's lineup during the WRGP. After Andre loses to Yusei, Breo takes over and begins to brutally weaken him with his Deck Destruction Deck. Jean explains that Breo has an unfailing memory, and that has allowed him to remember vital parts of Yusei's strategy.
Breo Summons his "Voltic Bicorn" early in the Duel, and with his Mill Deck he succeeds in leaving Yusei with a Deck of only five cards. However, Breo decides to fight for the team, and loses to Yusei after inflicting some parting damage. Breo leaves the fight to Jean, who now has a huge advantage because Yusei only has 1000 Life Points and five cards in his Deck.
After Team Unicorn's loss to Team 5D's, they face Team Catastrophe in their second round. Breo has now switched to "Last Wheeler", while Jean is "Second Wheeler", most likely to use the Deck Destruction strategy to finish off opponents. Unfortunately, this goes awry, as both Andre and Jean crash unexplainably, and as such, forces Team Unicorn out of the WRGP.
Breo sees off Jean and Andre to hospital, and then provides Team 5D's with information collected during each of their Duels with Team Catastrophe. Breo watches Crow and Jack Atlas Duel Team Catastrophe, and is shocked to discover that the card that caused the crashes was "Hook the Hidden Knight".
Breo is also present when the Diablo are being released upon the city.
Breo was seen when Yusei was remembering the powerful teams that he had to face in order to get to where he was whilst he was Dueling Jakob in the WRGP finals. He was also seen when Yusei was Dueling Z-one, cheering Yusei on to win.
He is later seen at the WRGP where he had become a member of Team Unicorn, he defeated Toru but was then taken out by Misaki who then in turn was taken out by Andre. Although the player can't Duel Breo during the events of the storymode, he is able to Duel against after the player has defeated Team New World and beat the story mode. He is located in the left side of the pits in the New Domino Stadium standing along his team mates.
Breo's Turbo Deck is a Bicorn/Beast Deck focused on milling the opponent's Deck in order to win. His Deck is spearheaded by "Voltic Bicorn". He also uses a large array of Trap Cards to negate his opponent's moves so that he can freely go about with his strategy without worrying about taking damage.