Luca

Luca, along with her twin brother Lua, aid Yusei Fudo, whom they adore and support in his duels while making fun of fate. Luca is calm and collected.

Luca is able to communicate with Duel Spirits following an incident eight years before the Fortune Cup. She was revered as a duel prodigy at the young age of three and while duelling, collapsed, falling into a coma that lasted a month. The cause of the coma was her spirit leaving the human world and entering the world of Duel Spirits, meeting Ancient Fairy Dragon who spoke of impending danger in the years ahead. Naïve to the true extent of what was to come, Luca promised the vulnerable Duel Monsters that she would stay, only to wake some time later.

Despite being the Signer bearing the Front Claw [Rear Claw in the dub], Luca doesn’t hold the dragon that fulfils her position as one of the legendary five. What she learns through a dream at the time Godwin explains the legend to Yusei is that Ancient Fairy Dragon was captured by the dying Uru at the end of the previous conflict 5000 years ago and forced inside the cliff face that she saw when her duel with Frank in the Fortune Cup returned her to the world and restored her memory of the promise. During the tournament, despite early uneasy feelings around Yusei, she bonds with him. Her Birthmark is revealed and confirmed by Yusei during her duel with Frank in which he is able to send her to the Duel Spirit World in the hope of taking it over, Yusei is the one to catch Luca when she returns, able to fight on after hearing Lua’s pleas for her to fight, her brother unable to completely cross over.

Season 2

[Spoiler] After the tournament, Yanagi and Himuro become somewhat guardians to the twins and escort them to a dinner party at the Arcadia Movement that Divine invites them to after Yusei’s return to Satellite. However, Divine sets his sights about including Luca in the Movement, using Lua as bait and to test the boy’s skills. After he falls to Divine, Lua remains unconscious and Luca stays by his side until Himuro and Yanagi arrive, aware something is wrong after the two Games of Darkness begin in the building. Luca senses Aki’s presence as an active duellist and leads the others to witness some of her duel with Misty Lola.

When the Earthbound Gods Aslla Piscu and Ccarayhua are summoned, Luca’s Birthmark activates and creates a shield around the group, revealing to them that the Birthmarks have the power to protect people from the soul-absorbing power of the Earthbound Gods. Luca and Lua watch from the outside as the duels end and Aki remains comatose. They join Yusei, Jack and Aki as they visit Godwin where Luca defends Lua’s presence despite not being a Signer, threatening Godwin that she will go nowhere without him.

Luca’s real challenge comes in Satellite after the Signers split up where she is transported to the Duel Spirit World, leaving Lua to volunteer to fight Demak who holds Ancient Fairy Dragon, the card Hakase Fudo dropped during his escape from Rudger’s security, leaving the later Spider Dark Signer to retrieve it. Luca meets with Trunka, an elderly mage who has been turned into a young boy by the effects of Zemon, the Demonic Monkey King, and the staffs his goons wield. In the process of escaping, Kuribon - Luca’s faithful spiritual partner, Sunlight Unicorn and Sunny Pixie sacrifice themselves in order to protect Luca.

She and Trunka venture out to find Regulus - a loyal servant of Ancient Fairy Dragon - who has one of the staffs around one of his hind legs. Because of the staff, everything Luca pleads is reversed into threats directed at Ancient Fairy Dragon, enraging him until he chases them to a large log over a raging river. Again, her pleads for help fail and the three fall from the log and into the river. Raising her arm to signal Regulus, the lion notices the Birthmark on her arm and overrides the Minus effect, the staff breaking loose from his leg. As they head over the waterfall, Luca uses the Minus staff in her possession to reverse the flow of water and drag them back into the river.

As they approach Zemon’s castle, Luca notices that her clothes are getting larger - the Minus effect is affecting her as well as everyone else. She plots to enter the castle pretending to have captured Regulus in order to get to Zemon. The plan is a success and she witnesses Zemon beginning to release Ancient Fairy Dragon until Trunka accidentally exposes them. Regulus and Power Tool Dragon, on Lua’s side of the battle, destroy Zemon simultaneously, reverting everyone back to their true selves. Trunka sends Luca back to the human world.

Returned to the battle field just as Lua hangs over the brink of defeat, Luca takes it upon herself to complete the battle with Lua and Power Tool Dragon by her side. Demak has Ancient Fairy Dragon come to the field, only for Luca to later gain her, Regulus severing the chains that bound the captured dragon. Together; she, Power Tool and Ancient Fairy destroy Demak’s Earthbound God - Cusillu, the first to fall. Regulus and Ancient Fairy Dragon thank her before they appear in her hands as cards.
After the duel, Luca stays with Ushio, Lua and Yusei - who has deviated from his journey towards the Giant Tower - as they witness all but Jack’s duels to bring down the Earthbound God. During the final battle, Luca summons Ancient Fairy Dragon in order to hold off the Underworld King’s minions who threaten Yusei, Jack and Crow. [/Spoiler]

Season 3

[Spoiler] Six months after the Signer War and Luca and Lua have returned to Duel Academy along their friends Tenpei, Patty, Bob and the outsider Sly. Luca reaches out to Sly, but he seems reluctant to take part in their friendship. During a journey with Lua and Tenpei into a forest, Luca comes across a mansion and enters, despite pleas from Kuribon and Regulus. There she meets Michael, a boy who stays by his sister, Claire’s side. Luca soon learns that the mansion is the site where people have vanished and watches on as Lua duels Michael to save her from becoming another victim.

After the landing of the Skiel tablet, Lucciano enrolls in Duel Academy and catches Luca’s eye. She quickly befriends him and learns about his D-Board, the tool underage duellists can use for Riding Duels in the place of a D-Wheel. Lucciano teaches Luca how to use it and she finds Lua practicing on a highway later on after he has Yusei build him one. As they play, a boy intervenes and drags the two into a duel. Luca learns that the boy is none other than Lucciano and fights back with Ancient Fairy Dragon. However, his Infinity monster attempts to capture the dragon, stopped only by Lua’s interference. Despite their impressive duelling, both twins are defeated by Lucciano, but without any losses, to Luca’s relief. [/Spoiler]

Much like Yugi Muto and Judai [Jaden] Yuki, Luca has a spiritual partner in the Kuriboh family - Kuribon. Her role in Season 3 is reduced as a result on the focus of Riding Duels and the elder Signers and companions.

[Spoiler] In the manga, she seems to be influenced by a Card of Darkness and works as a duel assassin under Godwin. She holds the manga equivalent of Ancient Fairy Dragon, Ancient Pixie Dragon. [/Spoiler]