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Leo's outfit is similar to his sister's; it consists of a short-sleeved white jacket over a sleeveless dark blue shirt with golden markings that differ from Luna's shirt. He also wears white shorts with a dark blue belt and blue sneakers of the same color. Leo also has a bracelet on each wrist, and his blue-green hair is pulled into a single, high ponytail with two shoulder-length bangs on both sides of his face but when he doesn't wear it up (like when he's sleeping) it looks like Luna's in the same situation. He carries a [[Duel Disk]] with a blue and white trim on his left arm, which was originally too big to fit until [[Yusei Fudo|Yusei]] modified it.

After Yusei's Duel with [[Kalin Kessler]], Tanner and Yanagi arrive at their home as they discuss the current situation. They are worried about whether Yusei had already fought against a Dark Signer or not. Then he asks Luna if it's true that "[[Power Tool Dragon]]" battled alongside the other [[Five Dragons]] against the [[Earthbound Immortals]], to which she responds that it may have. Leo immediately assumes himself to be the Fifth Signer and proclaims that he must also protect Luna as well. Yanagi reasks and Luna says she only said yes to cheer up Leo.

Leo also learns that Sayer plans to use his psychic duelists as soldiers in a war against the world for all the discrimination they have taken. As the Duel progresses, Sayer attacks Leo directly, making him cry, however he tells him not cry and instead fight. Due to the fact that he has revealed his true purpose, Leo's life is at stake now, and in order to save himself, he must awaken his hidden abilities.

After the building begins to collapse due to the Earthbound Immortals' assault on it, Tanner takes the two of them outside to safety. After Akiza lands in the hospital in a comatose state, Leo, along with Luna, as well as Jack are present within. As with the rest of the people there, he witnesses the duel between Yusei and Akiza. After it concludes with Yusei's victory, Leo tags along with Luna and the other Signers as they are invited by [[Rex Goodwin]] into his place, as he wants to reveals to them some secret concerning the [[Crimson Dragon]], as well as some sort of deep connection between them and the [[Dark Signers]]. There he learns about their own "fate" which is responsible as for that the Signers to have met in someway. Leo finally learns that the Fifth Signer was already awakened long ago and that it will appear later on, and also about the Dark Signer's true identity involving the Netherworld, their abilities, and use of [[Earthbound Immortals]].

Afterwards, the Dark Signers perform some kind of dark ritual within Satellite, not only enclouding but also somehow vanquishing its other Satellite residents. Because of this, the Signers, along with Leo and [[Mina]], all board a helicopter to Satellite being flown by [[Trudge]] himself. When they all arrive to Satellite they are greeted by [[Martha]]. However, the reunion is cut short as Yusei finds out that Rally, Crow, and the others have disappeared. Later during dinner, Roman suddenly appears, demanding to Duel. As Yusei accepts to Duel, accompanied by Akiza, Jack and everyone else take Martha and the kids to a safer place. As Roman and Yusei's [[Shadow Duel]] is about to begin, Luna, Leo, and Jack become aware of it as their Marks of the Dragon began to react.

They then see the Condor geoglyph that has appeared on the sky. The King of the Underworld Netherworld not only revives, but also is heading towards the formed Condor geoglyph, which is over New Domino City. However, the Crimson Dragon appears once again to take everyone to Rex Goodwin's mansion. Where he reveals to them his identity as the final Dark Signer and then declares that a Shadow Turbo Duel will be held within Condor geoglyph as a ritual to welcome the King of the UnderworldNetherworld.

As Yusei, Jack, and Crow accept the Duel in order to stop the resurrection of the King of the UnderworldNetherworld, Leo cheers for them along with his sister and the rest of the people who can only support them by watching while hoping they win.

After discovering that the Antinomy was Bruno, Leo and the others continue deeper in to the Ark Cradle in order to confront its final resident - Z-ONEone. After they found Z-ONE one who have waiting for their coming, at this time Leo discovered that backside of Z-ONE one exactly same with the back side of Yusei Go.

Leo and his sister are known to be together in almost every scene of the show (not included in the Fortune Cup) and have an extremely close bond. Throughout the entire show, it is made apparent that in every situation involving [[Luna]], Leo is the one to give her the strength to fight back. Even though Leo appears to be completely ordinary, when his sister goes to the spirit world, he is somehow able to communicate with her. It is said that when Luna went into a coma state when she was 3, Leo was the only one that believed she would awaken, and was said to be the one that awoke her from the spirit world. So far, only Leo has been able to awaken Luna when she goes to the spirit world. Luna is the most important person in his life and he will protect her at any cost from dangers; to Luna, Leo is her 'hero' and she can't live without him. The possibility for Leo being the only one to awake her from the spirit world is because he might have some of the abilities that she possesses. It is a known fact that Leo and Luna go together to [[Duel Academy]] along with [[Dexter]] and their teacher [[Miss Bartlet]]. Even though the twins have their ups and downs they love each other dearly and are considered the most valuable person in the other's life. When they were battling [[Devack]] and his [[Earthbound Immortal]] he said he wanted to show that he can protect his sister from harms way including from Devack and Luna tells Devak Devack she will never forgive him hurting the person she cares about most in the whole world. He also feels that he is useless and can't protect her from harm but Luna says she needs him. In the original he said she was a bother to him while in the English dub he said she was holding him back. In the duel with [[Aporia]], after Luna got knocked out from [[Machine Imperial Soldier Grannel Ein]], it had a devastating effect on him similar to the first of Aporia's embodiment of despair [[Lester]] had his parents lost. This duel further affects him in his confidence of protecting Luna, while at several parts of the duel Aporia counters all of Leo's moves leaving both Jack and Luna close to death. This makes him to force himself to be stronger and literally put his life at risk to protect Luna, best demonstrated by using [[Double Ripple]] to summon Ancient Fairy Dragon in defense mode for Luna, which costs him his life (for a brief moment) and was reborn as the Sixth [[Signer]] with [[Life Stream Dragon]].

In episode 13, Leo is shown to admire [[Jack Atlas]] from the time the latter reigned as King. He has figurines of Jack and his "[[Red Dragon Archfiend]]", but now thinks of Yusei as the better Duelist after the [[Fortune Cup]], much to Jack's annoyance. Even if he does, Leo was inspired by Jack to become a great Duelist.During the duel Against against Aporia Jack notices something new about Leo and said that leo Leo would protect anyone at any cost even if it means giving up his life.

Leo looks up to [[Akiza Izinski]] as a Duelist, even when she went under her alias, the "Black Rose Witch". Although he was somewhat scared of her, he still admired her abilities. He wants to be ranked at the top of his class like she is. He also relied on her to stand up for their right to duel in [[Duel Academy]].

Leo plays a '''[[Morphtronics|Morphtronic]]''' Deck that features an [[Archetype]] of monsters known as "[[Morphtronics]]" whose effects are dictated by [[Battle Position|battle position]]. The monsters' appearances are derived from various objects such as cell phones, pen drives, cameras and magnets. His Deck also specializes in summoning his strongest card, "[[Power Tool Dragon]]", and the use of [[Equip Spell Cards]].

During the 3rd Arc of the Series, at the Duel Academy, he uses [[Swordsman of Landstar]] (or possibly [[Comrade Swordsman of Landstar]]) and [[Marauding Captain]]. Though it is known that Leo was only using them at the time because the lesson is based on [[Warrior]]-Type monsters. So, like Dexter, their Decks were revolving around this type of monsters for practice only.