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.

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.