"Luna" translates to "moon" in a number of languages descended or borrowing from Latin, which features "lūna". In ancient Roman religion and myth, Luna is the divine embodiment of the Moon. In the manga, when Luna first meets Shark, she introduces herself as "a messenger from the moon". Her Moon-style Deck, D-Pad and Duel Gazer refer to these facts.
Luna appears to be one of the few humans who can hold a "Number" card without being possessed by it. The pendant which she wears on her chest is possibly another of Dr. Faker's creations; by pressing it, Luna was able to deflect Kaito's Photon Hand, as well as teleporting herself, Shark and Yuma in an instant to a far distance.
Luna previously worked on Dr. Faker's side, assisting him, but later betrayed him. She explained that he was once a good scientist whose goal was to develop an energy system which would not harm this world, but a certain incident made him change. In a flashback, she is seen watching when Shark was unfairly disqualified from a tournament, taking the blame for Kyoji Yagumo. She seemed to be working on the tournament (which was sponsored by Mr. Heartland) as part of its staff.
She soon reveals and introduces herself, and says that Shark can call her an emissary from the moon. Shark replies saying that looks like something straight out of a fairy-tale, but that he doesn't hate them though. Luna says that she doesn't have any rancor against him, but that she must face him. Then, they begin a Duel.
The Duels ends quickly, with Shark defeating Luna in an O.T.K. After he wins, Shark asks Luna if she is alright; she is impressed that Shark could Summon 3 Xyz Monsters at once during the Duel, and says that she wasn't wrong. Luna reveals she is a Number Hunter whose goal is to eliminate the "Numbers", and says that Shark is the only one who can stop Dr. Faker, and for that he needs the power to do so - a "Number". Shark declines, saying that he was already once possessed by a "Number", and that he cannot do so. However, Luna replies that Shark knows how terrifying a "Number" can be, and that this is just why it would be okay. She further explains that "Numbers" are mirrors that reflect the hearts of the people, and at that time, his heart was full of darkness, but Yuma and Astral freed him from that darkness. She then gives Shark a mysterious card, and says that it is a new power to protect him.
After Shark defeated a store owner and he was confronted by Yuma, Astral, and Kaito, Luna, still cloaked, walked up, explaining that Shark was hunting "Numbers" because she told him the truth. She removed her hood, and greeted Yuma and Astral, calling it a pleasure to meet them (and revealing that she could see Astral). Kaito recognized her, and she introduced herself, explaining that she used to assist Dr. Faker. Yuma was shocked, and asked why she was with Shark. Luna explained that she'd asked Shark to obliterate the "Numbers." Yuma protested that their power wasn't bad, and Luna responded that that wasn't the problem, their very existence was. If such a thing existed, people would fight over it, and that fight would destroy the world. Yuma protested that she didn't know that, but Luna replied that the fighting had already begun. She stated that Dr. Faker and Mr. Heartland planned to destroy the Astral World, as well as this one, asking Kaito to confirm it. She sadly remarked that for his brother Haruto's sake, he couldn't disobey those two, calling him a poor little puppet.
Kaito angrily told her to be quiet, claiming that he didn't need her pity. He tried to take the duo's "Numbers" and souls with his Photon Hand, but Luna deflected the attack with her pendant, telling Kaito that that tactic wouldn't work on her, teleporting herself, Shark, Yuma and Astral out of the range of Orbital 7's power at the outskirts of Heartland City. She then departed with Shark, telling him that it wasn't yet time to fight Yuma and Astral. 
Later, she and Shark stood on top on an unfinished building. Shark told Luna that thanks to her and the card she'd given him, he saw something interesting, Yuma, Kaito and Astral. Luna stated that all the players were in place, but Shark replied that they were all in place except for him. He asked her to tell him the truth, which was why he'd argeed to help her. Luna mused on Kyoji Yagumo, the one who changed Shark's fate. After Shark had remebered his time with Yagumo, Luna admits that when she saw the incident, she knew that he'd taken Yagumo's crime upon himself when he'd dropped the Deck he'd stolen. 
When Yuma was challenged by Eviluder, she and Shark watched from the top of a nearby building, and she asked Shark if he was just going to sit and watch. Shark replied that then wasn't the time to move. Both then noticed Kaito and Orbital 7 on a nearby roof. When Eviluder called out his "Battle Eagle Tokens" she noted that he was a powerful "Numbers" user. She was shocked when Yagumo, the new Numbers Hunter, appeared in the air above them, and after he punished Eviluder, declared the Numbers War and left, she left with Shark, telling him that they shouldn't do anything foolish then.
Luna was with Shark when he defeated Shadow. Shark said that that didn't take much, with Luna telling him he is modest, and explained that he is too strong for his opponent. Shark explained that Kyoji isn't careless, and that he didn't see him challenging them directly. Luna said that Dr. Faker is a mad scientist bent on destroying both the Astral World and this one, and that Kyoji's heart must be deep in shadow if he is willing to help him. Curious, Shark said that he never asked Luna why did she help that mad scientist. She explained that Dr. Faker was once a good scientist whose goal was to develop an energy system which would not harm this world. Shark asked what happened then, with Luna explaining to him (the explanation is not shown). Shark said "so that's Kaito's background...", with Luna explaining that in order to stop Dr. Faker from destroying both the Astral World and this one, he would eradicate the "Numbers", no matter who stood in her way.
One day, Kaito appears to challenge Shark, who was with Luna. She watched as both Dueled, and called Shadow a cheater when he triggered his "trap" for them. When Yuma steps up to help Shark and Kaito, Luna is very surprised by his deed, and wondered if he was doing that for them because he was that confident or just an idiot. When Yuma was about to lose but still intended to give his own Life Points to protect Shark and Kaito, Luna thought that Yuma is an incredible boy, and wondered what kind of Duelist would go that far for someone else. After the Duels ended and Shadow was defeated, Yuma fainted. Shark told Luna they should take Yuma to their hideout, surprising Luna. He further explained that despite being his enemy, Yuma saved his life, so he couldn't just leave him there, with Luna agreeing. They then take Yuma to their hideout, where they explain to him the reason behind the Numbers War.
Just a few cards of Luna's Deck were shown, but in her Duel against Shark, she used a stalling strategy combined with "Kachi Kochi Dragon". Also, her monsters are themed after the Moon rabbit legend, making a reference to her name and sobriquet.
|Moon Gardna (ムーン・ガードナー Mūn Gādonā)|
|Moon Magician (
|Kachi Kochi Dragon (カチコチドラゴン Kachi Kochi Doragon)|
|Level Denial (レベル
|Rank Drop | Rank Denial (ランク
- ↑ 1.0 1.1 Yu-Gi-Oh! ZEXAL Rank 19: "Messenger from the Moon!!"
- ↑ 2.0 2.1 2.2 Yu-Gi-Oh! ZEXAL Rank 20: "A Three-Way Battle!!"
- ↑ 3.0 3.1 Yu-Gi-Oh! ZEXAL Rank 29: "Clash of the Champions!!"
- ↑ 4.0 4.1 Yu-Gi-Oh! ZEXAL Rank 21: "Kyoji Yagumo!!"
- ↑ Yu-Gi-Oh! ZEXAL Rank 18: "Kaito Again!!"
- ↑ Yu-Gi-Oh! ZEXAL Rank 22: "Commander!!"
- ↑ Yu-Gi-Oh! ZEXAL Rank 23: "Menacing Force!!"
- ↑ Yu-Gi-Oh! ZEXAL Rank 24: "The Numbers War!!"
- ↑ Yu-Gi-Oh! ZEXAL Rank 31: "Save Your Friends!!"
- ↑ Yu-Gi-Oh! ZEXAL Rank 32: "The Power of Believing In People!!"