He is Luna's twin brother. Luna is younger sister, and he always wants to protect Luna. And he always want to help others, but that mind is too much. So Luna saying Leo's this mind is 'disease'. He saw Yusei and he hid him. He think he maybe Signer, but he wasn't so he was despaired of it. But when he with duel Aporia with Jack, Luna, he became sixth signer. He's deck is "Morphtronic". And he is team 5D's member with Yusei, Jack, Crow, Akiza Izinski, Luna, and Bruno.