Yu-Gi-Oh! 5D's Ride 22: "Duel Dragons!!"
Unlike his anime counterpart, Leo in the manga is quite sadistic and dark. His appearance and personality are both wild and malevolent, judging by the way he enjoyed crushing Aria, easily winning the Duel, and laughed when his dragon almost killed two people in the audience.
Leo's design is almost exactly the same as his anime counterpart's, except for his facial expression and eyes, which appear much more wild and malicious.
In the past, Leo and Luna were left by their parents to fend for themselves. Luna had a serious illness, which required large amounts of extremely expensive medicine to treat. To maintain a constant supply of these medicines, Leo and Luna both delved into the world of underground Turbo Duels in order to obtain the necessary money.
At first, they were a raging success and made large profits, but they were eventually beaten. After the loss, Luna became seriously ill, leaving her brother to duel by himself. Being alone made Leo's performance significantly worse, causing him to lose even more duels. Angry fans of his, who had lost money in bets on the outcome of his Duels, ganged up on the boy and dealt him a harsh physical beating. When Leo couldn't take any more, he fell to the floor and cried out, only to look up and see Lazar holding out the Machine Dragon - Power Tool card, and offering Leo a place as an eliminator in order to pay for his sister's medicine treatment. Leo accepted the offer and took his place in the D1GP.
Leo is first seen riding on his Duel Runner along with his sister whilst dueling Aria. Leo easily defeats the Duelist with "Machine Dragon - Power Tool". After his dragon's attack defeats Aria, some of the screws from the Screwdriver Missile shoot towards some spectators. Before they can hit, Crow Hogan summons his "Blackwing Tamer - Hawk Joe" to intercept the attack.
It is later revealed that Leo and Luna are eliminators hired by Rex Goodwin.
Yusei later challenges Leo and his sister to a duel in order to find out more about the Duel Dragons. As the duel progresses, Leo gains the upper hand by swarming the field with his sister's Forest monsters as well as summoning his ace, Machine Dragon - Power Tool, and powering it up to 4800 ATK. Although the duel seemed to be in Leo's favor, he let his anger get the better of him and filled up his Spell & Trap Card Zone with Equip Spell Cards and Continuous Trap Cards, preventing him from Setting the Dark Bribe in his hand. This allowed Yusei to win through a combination of Synchro Nova and a Gravity Warrior with 7100 ATK. This defeat simply angered Leo and his sister before they drove off.
Later, Leo and Luna are shown to have passed to the tournament's second stage. Their first opponent was Tetsu Trudge, but the twins defeated him with ease. Luna even called him weak.
Next, Luna is reading a fairy-tale book. She comments on the book like if it was a real story, and says that she must defeat the "dark wizard". Leo sadly notes how she is acting strange. Goodwin then appears to them as a hologram. He tells them that they must defeat the "dark wizard", and Luna realizes he is Yusei. Leo asks if that will bring Luna back to normal, and Goodwin confirms it. However, Goodwin's plans are only to test Yusei's Duel Dragon's strength, and for that, he needed to use another Duel Dragon. Leo and Luna then go after Yusei.
Like his anime counterpart, Leo uses a Morphtronic Deck, though it uses different members of the archetype. The Deck also includes some of his sister's cards, so that both Dragons can be Summoned. Those cards can also be treated as "Morphtronics" through the use of "Deformerize".