Luna

Luna, aka Ruka or Luca in the Japanese version. She is Leo's fraternal twin sister, and a Signer who possessed the front claw Mark of the Dragon. She and Leo aid Yusei Fudo, whom they admire and support, in his Duels.

Luna tends to get tired right after a Duel. She has the ability to communicate with Duel Monsters after having spent ample time with Duel Spirits in a different dimension during a coma. Much to her brother Leo's irritation, she tends to candidly point out the various flaws in his plans, but does deeply care for her brother.

Background
Luna lives together with her twin brother Leo in the Tops residential area. They spend most of their time alone together as their parents are usually at work. They were initially educated via the internet, so they spend most of their time inside. Later they went to the Duel Academy.

Luna has been Dueling since the age of three. Once, she lapsed into a coma after a Duel, and did not awaken for a month.

During that month, her mind lived in the Duel Monsters Spirit World under the protection of Ancient Fairy Dragon, one of the Signer Dragons. Before waking up, she promised she would always be there to defend the Duel Spirits from evil that threatened the land. However, the pressure from undertaking such a task alone was too much and Luna had to forsake her promise, allowing the Duel Monsters Spirit World to fall later into the influence of Zeman the Ape King, who without much difficulty with the help of his army, turned most of the spirits into stone, and eventually imprisoned them. He was even able to capture and rock-seal Ancient Fairy Dragon's spirit into the mountains. Luna later returns and saves the spirits with some help from Leo.

Personality
Luna is the younger, frail, calmer, more collected of the twins (in the english version this is changed to her being somewhat snobby, and tends to insult Leo, but she becomes more nice to him after the Dark Signer war and starts to act more like her original counter part).

Appearance
Luna's usual outfit is similar to her brother Leo's, consisting of a light pink short-sleeved jacket over a long-sleeved red shirt with golden markings. She also wears light purple shorts with a red belt and sneakers with black and pink markings and high socks. She has gray-gold eyes just like her brother.

On formal occasions, Luna wears a pink dress, a white cardigan and a pink ribbon below her neck. When she's sleeping, she wears pink pajamas with a nightcap. If at school, she wears the New Domino academy girls uniform with a red bookbag.

Luna's green hair is done up in two high ponytails on either side of her head with two shoulder-length bangs on both sides of her face.

Her Duel Disk has a pink and white trim. It was modified by Yusei to fit her left arm.

Abilities
Luna has the unique ability to sense and communicate with Duel Monster Spirits. Her most knownable spirit partners are Kuribon, Regulus and Ancient Fairy Dragon.

In addition to her connection with Duel spirits, she has also been able to travel to the Duel Monsters Spirit World at the risk of having her body comatose in the real world (with the exception of when Regulus cast a spell to transfer her to the Spirit World in the Dark Signer Arc).

She also has an ability to sense someone at times when they're in danger, such as when her brother was against Devack and in pain, or when Yusei was being shocked by officers near her house. In addition to this, she can feel or sense a persons Deck, such as before Yusei woke up, and Akiza's first Duel in the Fortune Cup where she could feel Akiza's Deck suffering.[9][10][11][12]

Yu-Gi-Oh! 5D's Manga
Both Luna and Leo were left to fend for themselves at a young age. In order to acquire money, the pair began to compete in Turbo Duels, even against adults where they were a raging success. But this was short lived as Luna fell ill, leaving Leo to Duel by himself. After losing, Leo was threatened by Nicolas as he couldn't afford to pay his side of the bet, leading to him getting beat up. Lazar witnessed this and promised to help Luna in exchange for Leo to undergo the Duel Dragon ceremony, which he accepted; acquiring "Power Tool Mecha Dragon" in the process. Some time after this. Luna underwent the same ceremony, acquiring "Ancient Pixie Dragon" as a result.

During the preliminaries of the D1 Grand Prix, Luna appeared with her brother, Dueling under the command of Rex Goodwin to find those suitable for "Duel Dragons". During this, they Dueled and defeated several duelists, including Aria. During this, Luna sat back and watched "Ancient Pixie Dragon" and "Power Tool Mecha Dragon" assault him, with the force of their Feel destroying his Duel Runner whilst Luna claimed that Aria was weak and boring. During the attack, one of "Power Tool Mecha Dragon's" screwdriver missles almost killed two innocent by-standers, but they were protected by Crow Hogan and his "Blackwing Tamer - Hawk Joe the Jet Black". Luna later observed Rex's speech to the finalists about the finals taking place in Satellite. In addition, he informs them that he dispatched Leo and Luna into the finals as only the best should remain.

Luna later appeared along with her brother, insulting Leo for thinking his name is important. The siblings were insulted by Crow who mocked that it was too late for them to be awake, but they merely brushed it off and insulted him back. When Leo revealed his "Power Tool Mecha Dragon" to Yusei and Crow, Luna was shocked to see that they could sense its shadow miasma. Leo then began a Duel with Yusei, where Luna informed him to not involve her as he started it. During the Duel, Luna insulted Leo's tactics, even to the extent that she threatened to harm him if he allowed Yusei to destroy her "Forest" monsters. She also asked Leo to let her get off of their Duel Runner when he transformed her monsters into "Morphtronics" via "Morphtronicize". As the Duel continued, Luna insulted Leo for bragging, telling him to shut up. When Yusei activated "Sword Dance", one of the blades struck Luna, which angered Leo, causing him to heavily assault Yusei, reducing his Life Pointss to 200. Yusei attempted to reason with Leo, but he vowed to destroy Yusei for harming Luna.

Yusei then proceeded to use his "Gravity Warrior" to take advantage of Leo's strategy, increasing its ATK to 7100. Luna notices "Dark Bribe" in Leo's hand, stating that Leo underestimated Yusei's strategy. She then insults his performance, stating that he dug his own grave. Yusei then speeds up, passing the twins and launched his attack. Before it hit, Leo stood up, preventing Yusei's sense from harming Luna. After the Duel, Luna insults Yusei, stating that the Duel was boring. She then informs Yusei that she's the only one who's allowed to bully Leo and proceeds to threaten him, emitting a shadow miasma. Seeing this, Leo tells her that they completed their mission before disappearing, telling Yusei they'll see him in Satellite.

The next day, Luna and Leo were present on the ship headed to Satellite for the finals. During which, they were enjoying the food provided until Crow appeared, insulting the pair for being happy, despite their loss to Yusei. This resulted in an argument which annoyed Luna at first, but she then joined in, insulting Crow's hair. An omake revealed that she watched an eating contest between Leo and Crow as they didn't have access to their Duel Runners to settle their argument.

Later, Leo and Luna are shown to have passed to the tournament's second stage. Their first opponent was Tetsu Trudge, but the twins defeated him with ease. Luna even called him weak.

Next, Luna is reading a fairy-tale book. She comments on the book like if it was a real story, and says that she must defeat the "dark wizard". Leo sadly notes how she is acting strange. Goodwin then appears to them as a hologram. He tells them that they must defeat the "dark wizard", and Luna realizes he is Yusei. Leo asks if that will bring Luna back to normal, and Goodwin confirms it. However, Goodwin's plans are only to test Yusei's Duel Dragon's strength, and for that, he needed to use another Duel Dragon. Leo and Luna then go after Yusei.

Fortune Cup arc
Luna was selected as someone to participate in the Fortune Cup. She was told she was randomly selected, but was invited so Yliaster could confirm that she is a Signer. However, not up to participating, Leo planned to disguise himself as her and Duel in her place.

Due to their Marks, Luna was able to sense Yusei when he was shocked by the police officers. She and Leo rescued him after his Duel with Tetsu Trudge and took him to their home. Yusei wanted to leave, feeling that he was putting them in danger, but Leo talked him into a Duel. After Yusei won, Luna and Leo 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 small arms.

The next day, Leo entered the Fortune Cup disguised as Luna, but using Zigzix's Signer-detecting technology. Lazar was not only able to determine that Greiger Dueled Leo instead of Luna, but also knows that Luna is a Signer.

Luna faced off against Professor Frank 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. Before she concludes the match, Luna is called a Signer by Frank, although unaware at that moment of its meaning or its relationship with her Claw Mark of the Dragon.

Only Yusei becomes aware of her being one, though he does not tell the others. Eventually, though, they learn this after his Duel against Akiza Izinski. She witnesses for the first time the appearance of the Crimson Dragon during Yusei and Jack Atlas' title Duel. Because of the Duel, Luna, along with the 3 other Signers, are transported to an alternate dimension. There they are shown 2 visions; one of the Stairway to the Dragon Star, where the People of the Stars were worshiping the ancient Signers, and the other showing Satellite being destroyed, and in its place the appearance of a spider mark shines.

After that, Luna and Akiza are the only ones to witness Jack's defeat. As they all return to the stadium, she reunites with Yusei in order to leave through an underground tunnel. Luna talks to Yusei about the vision, who responds that he doesn't know what it means, but that in any case he must prevent it from happening. She also asks him what is a Signer, to which Tenzen Yanagi intervenes in order to answer to her. Luna learns its meaning and its relationship with her along birthmark, along with the fact that that Yusei, Jack, and Akiza are Signers too.

Dark Signers arc
After the Dark Signers started taking action, Luna has been having vivid dreams of the Five Dragons and the Crimson Dragon battling an unknown evil. Ancient Fairy Dragon gets pulled into an abyss, showing that the Dragon's card is currently with the Dark Signers.

As Yusei is about to come face to face with Kalin Kessler, his Mark of the Dragon reacts along with Luna, Jack, and Akiza's. She notices this and Leo does too as he is nearby. Luna is able to sense that Yusei is the reason of why her Mark of the Dragon glows. After Yusei takes a hit by "Earthbound Immortal - Ccapac Apu", Luna's Mark of the Dragon gets etched onto her arm.

Leo explains to Tanner and Yanagi that Luna is frail and therefore she can't go out much. Luna accompanies Leo, Tanner, and Yanagi to the Arcadia Movement, where they meet Sayer. He induces them to sleep with gas, wanting to make Luna a member of the organization due to her powers. Luna wakes up next to Akiza, where they both watch the Duel between Sayer and Leo. Akiza tells Luna that Sayer wants to test her brother to find out if he possesses any similar powers. Leo passes out upon losing as Luna calls out to him.

After the Duel, Akiza informs her that Leo isn't in danger. Luna clarifies Leo doesn't possess any powers, but he was still kept in a place with Luna. Akiza tells her that in any case the Arcadia Movement will be her new home, as she doesn't want Luna to walk through the same path she did; the path of being feared and abandoned by others because of her powers. Luna asks Ancient Fairy Dragon for help, but her spirit says that she cannot rescue her and that she is witnessing the posing threat of the Dark Signers. In order to set her free, Luna must join forces with her servant, Regulus, who will eventually appear to her. Once Ancient Fairy Dragon is set free, she promises to protect Luna from the enemy.

After Bolt Tanner frees her and Leo, while fleeing the building, she senses Akiza in a Duel as her Mark of the Dragon begins to glow. As she decides to find her, the four of them run into Misty and Akiza's Duel. As Luna notices the lizard Dark mark, she recalls the vision of the battle between the Crimson Dragon and the Earthbound Immortals again. Right as Misty is about to Summon her Earthbound Immortal, Luna's dragon birthmark protects her, Leo, Bolt, and Yanagi from being sacrificed to Summon Misty's Earthbound Immortal. Tanner gets her and Leo out in time as the building collapses.

After Akiza lands in the hospital in a comatose state, Luna is there along with her brother and Jack. As with the rest of the people there, she witnesses the Duel between Yusei and Akiza. After it concludes, Akiza decides to help them in their fight against the Dark Signers. After it, Luna along with Leo and the other Signers are invited by Rex Goodwin into his house, as he wants to reveal to them some secret concerning the Crimson Dragon.

She learns from him that those who are Signers exist within some sort of "fate", derived from the Crimson Dragon's power, one which cannot be escaped from. That strange fate was the one responsible for that all of the four Signers to have actually met in someway. Thus, the "Fate of the Signers" unites each and every one of Yusei, Jack, Akiza and her own destiny together in order to guide them all.

Nonetheless, according to Goodwin the four of them are not only Duelists chosen by the Crimson Dragon itself, but they are also the reincarnations of the ancient Signers themselves. Also already predicted thousands of years ago the four of them would encounter one another. She also learns about the Dark Signers' abilities involving their powers and use of the Earthbound Immortals. According to Goodwin, their powers that manifest in a Duel come from the underworld. Also as they appeared on the city, many casualties occurred just like in Satellite due to their Immortals. Luna along with the others realize the shocking truth behind the transformation of an individual into a Dark Signer: It can't be reverted due to the fact those individuals are dead and that they are resurrected because of a powerful phenomenon occurring on the other side of the Underworld.

After this she cheers Leo up, who feels he can't be a hero or protect her because of having lost to Sayer, by saying he doesn't have to be a hero, and to just protect her like he always has.

Like Jack and Akiza, she's present along with her brother during and after Yusei's match against Roman Goodwin. After it concludes, the rest of the Dark Signers show themselves, as their ancient battle is about to commence. Later on as each one of the Signers is set on defeating their respective opponent, they split up to each of the four control units of the Original Ener-D Reactor. As Luna and Leo are taken by Trudge to where Devack is waiting, she instead travels into the Duel Monsters Spirit World in order to free Ancient Fairy Dragon. Due to this, Leo bravely challenges Devack to a Duel in her place, as he is determined to fulfill his promise of protecting her.

In the Spirit World, Luna enters the Minus World in search of Regulus. She gets chased down by an army of monkey spirits commanded by Zeman the Ape King, who is Devack's Dark Synchro Monster. The monkey army captures "Kuribon", "Sunny Pixie", and "Sunlight Unicorn". She evades them with the help of a spirit named Torunka. Luna eventually finds Regulus at Pojar Forest and tells to the Lion the promise long ago made to Ancient Fairy Dragon. However, because of the Cursed Needle in its ankle, he understands her in the opposite way. After a chase, Luna is finally able to dispose of the Needle and convince the White Lion of her righteous intentions by showing her Mark of the Dragon. After that Regulus, Luna, and Torunka set off to Zeman's castle. They are able to get inside by tricking Zeman into thinking that Luna is a servant of Zeman and has caught Regulus. She also tells Zeman to curse both Regulus and Ancient Fairy Dragon in order to minus Ancient Fairy Dragon completely. Zeman falls for this and is about to release her.

However, Zeman finds out they were trying to trick him and orders his army to attack them. He is eventually killed by Regulus, and at the same moment, Leo defeats him in the real world. Devack then Summons his "Earthbound Immortal Cusillu" and attacks Leo, who withstands the assault. Torunka sends Luna back to the real world, where she helps her brother. Devack then attempts to use Ancient Fairy Dragon against Luna, but she forces him to sacrifice it in order to save his Earthbound Immortal from being destroyed, which allows her to Summon her Dragon to her side of the field. Once this is done, Regulus appears and breaks the Dragons' chains freeing it at last. Luna then proceeds to use both "Ancient Fairy Dragon", equipped with "Pain to Power", and "Power Tool Dragon", equipped with "Rocket Pilder", to destroy Cusillu and defeat Devack.

After the Duel, Luna picks up "Ancient Fairy Dragon's" card, and she also discovers a "Regulus" Monster Card, indicating that he will return in a future Duel.

Following Crow's unexpected Shadow Turbo Duel against Greiger, Luna along with her brother, Trudge, and Crow himself witness the rematch between Yusei and Kalin Kessler. After the extreme Duel between the 2 finally ends, Luna, Leo, and Trudge accompany Yusei as he decides to go to the Original Ener-D Reactor directly in order to Duel against Roman one more time.

She watches the Duel between Yusei and Roman as it ends up with Yusei´s victory. After the Duel, she watches in horror as Roman blows up the bridge and drops Yusei into the Ener-D Reactor. Like the rest she´s glad, when Yusei returns, though unconscious. After he finally wakes up and that everyone eventually goes up through the same stairs they used before, they all notice purple sparks in the distance. She then knows that not only has Jack won, but also activated the third Tower.

Knowing that the last Tower to be activated is Akiza´s task, Luna along with Leo, Trudge, and Yusei all go to where it is. Arriving at an old and abandoned carnival, they split and began looking for her and Mina, except for the twins who look for them together. After Sayer awakens Akiza's power and is transformed once again into the Black Rose, they notice the tornado that has materialized on the carnival caused by the Synchro Summoning of "Black Rose Dragon". As they get to the area where the Duel is taking place, they both notice Akiza´s powers having once again manifested even stronger. After Mina and Trudge arrive, they all watch the outcome of the match, with Akiza emerging victorious. However, they notice that its too late for the last Tower to be activated, as the sun has already set.

The Condor geoglyph appears in the sky, while the King of the Netherworld revives from the Original Ener-D Reactor's crater. Kuribon appears to Luna, telling her that they mustn't let the King reach the Condor geoglyph. As the King begins moving towards it, the Crimson Dragon appears and transports Luna and her companions to Rex Goodwin's mansion, where the Condor geoglyph is located. Goodwin stands at the top of the Stairway to the Dragon Star, where he reveals himself to be the final Dark Signer and attaches Roman's arm to himself.

Goodwin declares that a Shadow Turbo Duel will be held within the Condor geoglyph as a ritual to welcome the King of the Netherworld. As Yusei, Jack, and Crow accept the Duel in order to stop the resurrection of the Underworld Ruler, Luna and the rest of the party cheer for them. However, when "Earthbound Immortal Wiraqocha Rasca" is Summoned, it tries to cheat by Summoning a flock of demonic black birds to attack Yusei, Jack, and Crow. Akiza and Luna are able to provide aid by manifesting Black Rose Dragon and Ancient Fairy Dragon to fight the horde.

World Racing Grand Prix arc
According to the third opening, it appears that Luna has enlisted into the New Domino City Duel Academy along with Leo. Dexter also accompanies them as the 3 of them are pupils of Miss Bartlet. After Yusei saves them from being expelled from Duel Academy, she goes missing in the Forest were people are reported to disappear. There, she meets Haley and he brings her to his house. Leo goes looking for her while Dexter goes to get Yusei. She is then trapped in the bedroom of Haley's sister, Claire. Luna finds out that Claire and Haley are actually dead, while Leo Duels Haley because Haley thinks Leo is going to hurt his little sister. When Yusei arrives, Leo asks Yusei to help Luna and leave him Dueling Haley. Yusei gets in and assists Luna. Luna wants to help the spirit of Claire who is still in the house and finds a special card. Leo defeats Haley and Luna is free. Luna gives Haley the special card and Haley and Claire disappear.

She and her brother appear to cheer up Akiza on her first day of riding a Duel Runner, and watch her progress. After that they follow Yusei and Akiza to a skating ring to learn some tricks on how use the Duel Runner. They both comment on whether it is a date or not between the two, and she agrees at some point.

When Lester enrolls in Duel Academy, he's admired by the students, especially Luna, though her brother suspects something odd about him and tries to keep a distance between him and his sister. Lester invites Luna to his home and shows her how to use a Duel Board. The next day she tries to practice with the Duel Board Lester gave her, and finds her brother practicing as well. But their fun is short-lived as Lester, in his Yliaster uniform, steps in and Duels the two of them, with Luna unable to escape due to her Duel Board moving on its own.

At one point in the Duel, Luna was almost blown off the track, but is rescued by Regulus, much to Lester's surprise. Lester quickly Summons his newly acquired monster, "Machine Emperor Skiel Infinity", to fight the twins. Luna Summons "Ancient Fairy Dragon" for the first time and inflicts some damage to Lester. But she's unaware of "Skiel's" frightening ability and it absorbs her monster. Leo Summons "Power Tool Dragon", but Lester quickly upgrades "Skiel" and attacks her brother directly, almost killing him, but he's saved by the Crimson Dragon at the last second (she also feels a piercing heartbeat for unexplained reasons). Luna then proceeds in Dueling Lester. He attacks her directly with "Skiel", but is protected by the physical attack of "Skiel" with the help of the monsters in her Deck. Lester escaped after the Duel ended. After that, the twins try to seek out Lester but every trace of him disappeared, even the mansion and the memories of anyone else who knew him. She, along with Leo, are members of Team 5D's pit crew.

Ark Cradle arc
After the finals of the WRGP, Luna, along with Leo, Bruno, and Akiza, are celebrating the victory of Team 5D's when the Divine Temple descends from the sky. When they learn from Sherry LeBlanc that Yusei will die if he enters the cradle, Luna cries, stating that she doesn't want to lose him. Yusei assures her that nothing will happen to him. She, along with the rest of Team 5D's, begin to travel to the Divine Temple. However, the gang gets split into three groups due to Z-one's trickery. She travels with Leo and Jack to the center of the temple.

Soon after splitting up, Luna, Leo, and Jack come across Aporia, who challenges them to a Duel where all damage to their life points becomes real damage to their lives. Luna and Jack are quickly knocked around by Aporia despite Leo's best efforts to protect them. As Luna is barely hanging on by 100 life points, Leo soon becomes Aporia's new target, unleashing as many card effects as possible on him. When Luna watches as Leo Summons "Power Tool Dragon" and "Ancient Fairy Dragon" to protect them and is assaulted by the effects of Aporia's cards which leads to his death, she begins to cry over Leo, and her life points begin slowly dropping due to Aporia's devices. In this battle, Leo finally awakens as a Signer. He then Summons Life Stream Dragon, which saves Luna and Jack by increasing their Life Points to 2000 with its effect. Luna soon realizes that Leo's new dragon is the one she saw in the vision of the 5,000 year-old battle she saw. Luna, Leo, and Jack then defeat Aporia with their dragons and head for the Support Gear.

After Yusei defeats Antinomy, she, along with Jack and Leo, reunites with Yusei and, inside the Support Gear, finds Z-one. During the battle against Aporia, Aporia himself realised that what he felt was not despair, but hope. Aporia appears in the Support Gear and Duels against Z-one to remind him of such hope. However, he loses. Realizing the power of Z-one's Deck and following everyone else's example, along with her brother, she gives Yusei her "Ancient Fairy Dragon" in order to help him in the final battle against Z-one.

Team 5D's Future
About half a year after the battle with Z-one, the twins receive a letter from their parents. In it, they tell them that they want to live together, but for that to happen, they may have to leave New Domino City. Luna and her brother are unable to decide what to do because they want to stay with the gang. After Jack challenges Yusei to a Duel and he agrees, the twins along with Akiza and Crow watch the Duel. Leo and Luna end up moving to be together with their parents.

In the next eight years, she loses her pigtails, and hangs out with some new friends at a school she attends.

Leo
Leo and Luna share a very close bond with one another. Leo is the only one so far to be able to reach out to Luna in the Spirit World, the first time doing it when she was 3 and in a coma in the real world. Leo believed she could still hear him that time, and woke up. When Luna was brought back to the Spirit world in the present, she didn't feel confident enough to protect it, but Leo vowed to protect her, while she protected it, and as a result she resumed her promise. They also look out for each other and help one another, as shown when Leo takes Luna's place Dueling Devack while she was in the Spirit World, and then does what she can after taking over for him. Luna has shown quite a few times that without Leo to support her, she'd be lost, and has even referred to him as her 'hero'. Their bond runs so deep that when her brother died against Aporia, she screamed in misery and also began losing Life Points through a weakened heart pulse. As Life Points were tied to the Duelist's actual life, it is proven with this that she would literally die without her brother.

When her brother was blown off the circut, and was saved, Luna put a hand on her heart thinking "But what was that, that feeling I felt from my heart?" (the english version drastically changed her words to "Thank goodness for the Crimson Dragon, he'll always save the day").

After Leo awakened as a Signer, Luna cried tears of joy, saying he would always protect her, and calling him her hero while looking at him adoringly. As the gang prepared to part ways, Luna comments on how much Leo has changed, stating that he's more of a man now, and referring to him as "big brother".

Yusei Fudo
Yusei has an older brother-younger sibling relationship with the twins. She was initially wary of him because of his criminal mark, and his status as an escapee from Satellite. The twins eventually warm up to him, and support him. After Luna woke up from her hypnosis by ending the Duel with Professor Frank. She collapsed, and Yusei carried her away from the Dueling platform. Yusei also showed concern for her during her Fortune Cup Duel. When she woke up after the fight with Frank and got out of Yusei's arms, she replied she was okay, and Yusei told her to simply do what she wanted in a kind voice.

Akiza Izinski
At first Luna seemed to have a cold feeling about Akiza. This was first shown when Akiza was Dueling in the Fortune Cup. Luna would state how she felt about Akiza's cards & how Akiza behaved. But she seemed to care for Akiza & thought that she was misunderstood. This is shown when she looks in disgust at the jeering fans who are cursing Akiza for being a witch. After Akiza develops a bond with the Signers, Luna seems to look up to her as an older sister figure, calling her "Aki-san". Her bond with Akiza also seems to have gone to her Deck when in season 2, she starts using Bird of Roses, Nettles and Spore.

Jack Atlas
Although not as clear as her brother, Luna does seem to hold some respect for Jack Atlas. Through the battle with Aporia, it is also evident that Jack to some degree worries for Luna, as her heart weakens, he angrily curses at Aporia for harming such a small child.

Ancident Fairy Dragon
The ruler of the Spirit World found Luna's spirit when she lapsed into a coma. Until she woke up, Ancident Fairy Dragon watched over her as if she was Luna's guardian angel. Luna vowed to protect the spirit world, but had to forsake that promise. She resumed keeping that promise after her Duel with Professor Frank. After Leo's Duel against Sayer, she turned to her for help. When she finally set her free during the Duel with Devack, she thanked Luna for keeping her promise and is currently by her side as a Synchro Monster in her Deck.

Patty
Patty is Luna's friend, usually seen hanging around her.

Lester
Luna was shown signs of having a small crush on Lester when he first enrolled at the Duel Academy as a normal student (this include her blushing and looking away flustered when Lester first smiled at her. Her crush on him is further evident, as Yusei pointed out with a slight smile that it was odd for someone like her to be giving someone so much praise like that). However it was proven to be short-lived, because after Luna found out that Lester was the one hurting them, she displayed anger, and some hatred, and even said after Lester almost killed Leo right in-front of her "Who'd be defeated by the likes of you!"

Knownable Relatives

 * Leo (Older Twin Brother)
 * Yusei Fudo (Surrogate Older Brother)
 * Akiza Izinski (Surrogate Older Sister)
 * Jack Atlas (Surrogate Father)
 * Yami Bakura (True Counterparts)
 * Ryo Bakura (Partnal-Counterpart)

Trivia

 * The Japanese names of the twins to be Rua and Ruka. However when their names appeared wrote out in the Japanese anime, they were Lua and Luca. The differing names is due to Japanese speakers pronouncing "L" and "R" as the same sound. When they Dueled against Lester and Aporia in the Japanese version their names were written as Lua and Luca
 * The 4Kids Entertainment website listed Luca's English name as Luna in the characters page, while Lua had his changed to Luka. Luka later had his name changed to Leo, while Luna's stayed as Luna.
 * The Russian word Ruka, or Рука, means hand or arm.
 * Luna's Japanese name, Ruka means "bright blue flower". Luna is an Italian name of Latin origin meaning "moon".

Voice Actresses

 * Japanese : Yuka Terasaki


 * English : Cassandra Morris (Episode 12 - Episode 64), Eileen Stevens  (Episode 65 - Present)