Name: Luca (Japanese); Luna (English)
First appearance: Yu-Gi-Oh! 5D's episode 12
Voiced by: Terasaki Yuka (Japanese);
Kether Donahue (English)
Known relatives: Lua (twin brother)
Resident: New Domino
Dragon Mark: Rear Claw
Dragon: Ancient Fairy Dragon
Luna lives together with her twin brother Leo in the Tops resident area, spending most of their time alone together as their parents are usually at work and are educated via the Internet.Between her and her brother, she is the younger twin out of the two. A child prodigy, Luna has been dueling since she was three years old. Once, she lapsed into a coma right after a duel, and did not awaken for a month. Upon waking up, Luna claimed she had been to the Duel Spirit dimension. This claim would prove to be true; for that month Luna's mind lived among the Duel Spirits, under the protection of Ancient Fairy Dragon, one of the Five Dragons. Before waking up, Luna promised she would always be there to defend the Duel Spirits from evil. However, the pressure from undertaking such a task alone was too much and Luna had to forsake her promise, allowing the Duel Spirit dimension to fall to an unknown force.
By present time, she and Leo rescued Yusei from Trudge after she sensed him being electrocuted by Security Officers, taking him to their home. Yusei attempts to leave so as not to get them involved, but the twins manage to get him to stay for the night. They awake the next morning to find that Yusei had left after modifying their Duel Disks to fit their arms. Although she knows what Yusei's reasons are for leaving them, Luna starts developing an interest in him and comments that she would like to talk to him more.
Luna was selected as someone to participate in the Fortune Cup. However, not feeling like participating, Leo attempts to duel in her place. The next day, he entered the Fortune Cup disguised as Luna, but using Zigzix's Signer-detecting technology, Lazar was not only able to determine that Krieger dueled Leo instead of Luna, but also that his sister is a Signer. Luna faced off against the Professor due to Rex Goodwin's consolation game but in the middle of the duel, both her and Leo are hypnotized. Luna's conscious self awakens in the World of Duel Monster Spirits, where she sees the degradation of the dimension and decides to uphold her promise from then on. When the Crimson Dragon appeared in the middle of Yusei's match against Jack, the four Signers were shown a vision of Satellite being destroyed by a mysterious spider drawing. After Yusei's victory, Luna feels somewhat disturbed about the vision the Crimon Dragon showed them and talks to Yusei about it. She is also having nightmares involving the dragons facing against a dark enemy, and the Ancient Fairy Dragon falling victim to its attacks.
She goes with Leo, Bolt Tanner and Yanagi to the Arcadia Movement to ask Divine for Akiza's help, but Divine gasses everyone, imprisons Tanner and Yanagi, forces Leo into a duel and holds Luna captive under the care of Akiza. She is told by Akiza that she should stay with the Arcadia Movement, as she would be doomed to be rejected by her family and friends for her powers. She contacts the Ancient Fairy Dragon for help and is told her servant, Regulus, will come to aid her. She and Leo are saved by Tanner and Yanagi and escape the movement as it is being torn apart by the Dark Signers. On the way out, they spot Akiza's duel with Misty, and a barrier comes out of her birthmark, protecting her friends' souls from being sacrificed when Misty summons her Earthbound God. She and the other Signers go to Goodwin to learn more about the situation, and they are currently deciding what they need to do.
Luna is one of the five Signers, the legendary duelists with the ability to summon the Crimson Dragon god. As such, she has the ability to talk to monster spirits and bears one of the Marks of the Dragon on her arm, in the shape of the dragon's rear claw. Its power links her to the world of spirits. It is also able to form a barrier around her and her allies to protect them from the soul-reaping effects of an Earthbound God summoning. Her dragon is Ancient Fairy Dragon, although the dragon's card is currently in the possession of Rudger.
Luna plays a Spirit / Fairy Deck, consisting of folkloric creatures and enchantments, such as unicorns and fairies.