Not much is known of her childhood, but it's implied she was abused as a child, stating to Renka she polished her skills and became a martial artist to fight back against her abusive parents. At some point, she became Diego Carlo's disciple and joined YOMI.
Rachel is a young fairly tall girl with long wavy blond hair down to her back and a very curvaceous figure and well-endowed breasts, both being as much so if more than any girl her age, including Miu and Renka. As a civilian, she usually wears her school uniform (that she modifies to be more revealing to show off her figure).
When she fights, Rachel wears her wrestling outfit for fighting that has arm bands with tassels on it with a revealing V-neck cover showing her breasts and has a very short skirt with tassels that reveals most of her legs and thighs. When she wants others to look at her, she tends to wear revealing outfits for attention.
Rachel has a very flamboyant personality, always wanting to be the centre of attention, which she often achieves. She easily becomes upset whenever others gain more attention than her and she claims they're "taking the spotlight" and is willing to perform anything to regain the attention of others, even if it means she embarrasses herself by ripping her clothes to do so, showing she's an attention seeker. Ethan said that as long as she has attention she does not care what happens to the world. She's selfish, spoiled, hot-tempered, and sarcastic. She's also a huge flirt, having Kenichi (unintentionally) grope her breast and teasing Kenichi about it despite it being an obvious accident and even kissed him on the cheek to make Miu very angry and even jealous.
She is also a very aggressive person and the more dominant of Team Gemini, often seen yelling, punching, and kicking her brother, and he, in turn seems very meek in front of her presence, despite their great difference in size. Despite this, Ethan loves his sister very much, but Rachel rarely shows any form of care towards her little brother.
Rachel seems to enjoy battle due to the attention it gets her, but is easily riled when an opponent grabs her attention, forcing her to beat the opponent in a very aggressive way. However, she usually holds back so as to create a more "spectacular" show in a somewhat sadistic manner and enjoys the suffering of others. She also follows her master's rule to fight only when there is an audience. Rachel also seems to have a penchant for humiliating other female fighters during a fight, as seen with the fight against Renka, where she subjected the girl to perverse submissions and in their second fight tried to take off Renka's swimsuit to embarrass her but showed disappointment that no one would see, showing clear signs of sadism and malice and even smiled at her cruelty towards Renka.
She displays the ability to manipulate and control the emotions of the crowd several times, an ability often exercised as she is always eager to be the centre of attention. Frequently used in this is the element of surprise, where she pretends to be beaten and launches attacks back at her opponent, thus getting the most attention she can.
However, Rachel has shown some (if any) level of compassion towards others, such as when Miu was kidnapped by Jenazad, she took pity on Kenichi and decided to help him and his friends locate her due to the Shinpaku Aliance saving her from him before. Also, her time with Kenichi and his friends seems to have helped her mellow out somewhat, as when Kenichi claimed she was a friend for helping him and the others save Miu from Jenazad, Rachel was shocked and even unable to understand the situation, thereby implying she's never really had a real friend nor does she understand the prospect of friendship.
- Luchador: Like her master, Rachel specializes in Lucha Libre, a style that uses powerful, yet overly flashy attacks. Despite Lucha Libre being a martial art with techniques that are considered to be overly flashy and completely useless in real close combat situations, she is able to effectively perform those techniques on her opponents with little to no effort at all. She is very adept in it and can take on grown men and several opponents on her own and easily win all the while showing off to the crowd and not even fighting them seriously. However, if their is no crowd to cheer for, Rachel reverts to a more straightforward style of combat, using simpler, yet exceedingly more powerful attacks. However the simplicity of this second style proved to be a weakness that Renka exploited in order to defeat her.
- Enhanced Strength: Rachel is very strong despite her feminine appearance, being able to take down grown men with little effort. She's also shown to easily harm her larger brother with ease (though Ethan usually can take a beating from most people).
- Enhanced Speed: Rachel is very fast, capable of keeping Renka on the defence for some time during their fight and even put her in a head lock till Renka was able to break free. Also, during her fight with Renka, she was able to create multiple after images of herself though they were only limited to her upper body and in close proximity to each other.
- Enhanced Manoeuvrability: Like Diego, Rachel is very adept to manoeuvring her body in and out the ring. During her first fight with Rachel, Renka noticed how she was able to read her moves in advance in a way similar to how Chinese martial artists do. Renka also noticed how flexible she is, as Rachel was able to perfectly counter her in a position that most fighters would not be able to do. Just like in her gymnastics class at school, she is able to break out of any hold anyone has on her with little difficulty and keep her opponents on the defence, which makes her a difficult opponent.
Yami/YOMI Saga EditKenichi defeat Radin with the other 7 Yomi members (Kajima Satomi was not introduced) .
Rachel meets Kenichi coincidentally and unknowingly at an underground fighting arena, where she managed to win 14 extremely difficult matches, but stopped when Kenichi started to receive more attention fighting than she did. She tried to fight Kenichi in a match and started to chase after him when he was pulled away by Apachai and Sakaki, but was stopped by Ethan, who showed her a picture of Kenichi. She later mentions that she and her brother are diamonds and that Kenichi was a priceless masterpiece made of clay that they will crush.
Rachel enters the D of D tournament with her brother as part of Team Gemini. During her time to fight, she makes an out-of-the-ordinary appearance with Mexican dancers and Mexican clothing. She first fought Dou Koukyoku, a practitioner of Nan Quan, who attacks first and quickly makes everyone believe she had the upper hand. However, this was all an act devised by Rachel, who wasn't in the ring and managed to put a flower on Dou's ear. Upon entering, Rachel quickly gained the upper hand and even taunted Dou for refusing her female characteristics, going as far as to tear her opponent's clothes to show her breasts. This backfires on her as she quickly loses the centre of attention, though she quickly takes out Dou and "accidentally" undoes her outfit to get attention. She is almost ambushed by Dou's teammate Kin but was saved by her brother. Rachel rages at her brother, having originally planned to pretend to get beaten and then have Ethan enter the ring and quickly take out Kin.
Rachel's next opponent is not shown but meets Tsutomu Tanaka, Team Gemini's next opponent, who proclaims his revenge against Ogata, and leaves because of Ogata's absence in the tournament. Rachel tried to pursue him, but is unable to see him as he disappears around the corner.
At the semifinals, Rachel and Ethan were both surprised to see Shō in the tournament. After witnessing Shō take out the Bufu team, Rachel is ordered to forfeit by Shō, so he could battle Kenichi. She refused and even tried to challenge Shō but was interrupted by the invasion of the island and the lack of an audience and her master's orders prompted her to retreat.
Rachel was one of the four YOMI members to transfer to Kenichi's school for the new semester and quickly makes an announcement upon taking the microphone. In chapter 269, she joined the gymnastic club with Miu, quickly gaining popularity in school. When Kenichi saw Boris she then snuck up behind him, Kenichi then noticed some one behind him, he then quickly got in a fighting stance, extending his palm forward, Mistakenly groping Rachel's breast, She then reacting by playfully saying he was a pervert. She then claimed to have taken a liking to Kenichi and kissed him on the cheek to make Miu jealous. During the school festival, Rachel was on the red team and was tempted by Chihiro Takashima to team up with her and embarrass Miu by pulling down her shorts. Her thirst for attention gets the better of her, however, causing her to throw and strangle her senpai, stating that Miu would be getting more attention if she did that. She joins the cheerleading squad and participates in other sports events, but does everything to get attention instead of trying to win, such as leaping across the equipment and landing on the bar in the pole vault.
Upon Kenichi's return to school after being beaten by Tirawit, Rachel is one of the classmates who participated in the camping trip. At the beach, she wears a different and very revealing swimsuit to show off her figure, to the point when other girls started to wonder if she was human. During the assassination of Ryozanpaku's disciples ordered by Alexander Gaidar, Rachel, followed by Ethan, attacks the soldiers under her own claim of listening to nobody but her master. With the threat finished, she resumes her school life, with Kensei advising her on methods to grab attention, such as jumping over a pole so that her breasts would bounce or going under it.Chikage being chosen to fight Kenichi, Rachel and her master made secret plans to fight him and a master of his choosing, threatening them Renka show up instead. She took on a variety of opponents including a trident user before her tag team match, frequently utilizing the element of surprise to get her attention at the utmost, and quickly forms a rivalry with Renka for getting attention during the tag team match. At first she just watches as the masters are unable to injure each other in the ring, but then decides to fight Renka outside of the ring, quickly drawing attention away from the masters' fight. She managed to do a pile driver and knock Renka down head first but was surprised at how fast she recovered uninjured. While fighting Renka, she subjected the kung-fu practitioner into a number of submission and grappling moves that gave Renka a hard time, but got parts of her body exposed, shocking her slightly, but discovered that this perverted revelation was Kensei's weakness and decided to tear Renka's clothes to give her master an opening, but backfires, as Kensei doesn't have the same reaction toward his own daughter. Realizing her master's seriousness and the removal of his Laughing Mask to unleash his Angry Mask, Rachel tried to keep the targets on the boat so that he could kill them while fighting Kensei. Rachel's battle with Renka was ultimately left undecided as she abandoned the fight on her master's command to point the camera at him while the masters' battle approached its climax, taking a few heavy hits from Renka in the process. She witnesses her master's loss and the revelation of his third Naked Mask. She attempts to attack Mikumo Kushinada, but is knocked unconcious and captured. One Shadow's protection. Rachel undergoes many tests on her performance, many of them similar to Shō Kanō's. The disciple-less masters consider taking her as their own disciple as it would be a waste of potential to dispose of her, especially Silkwat Jenazad, who commented that the 'green' (referring to her signature colour, not lack of expertise) of Lucha Libre was still strong in her, but said that it was possible to just pull the 'green' out.
After Kenichi defeats Ethan and Silkwat reverts his interest to fighting Sakaki, Rachel is the only exchange student still left at the school, and demonstrates her knack for rock music in a show, her ability of which is said by Siegfried to be raw, but with a lot of power, concurring with her Lucha Libre skills. She is also Kenichi's connection to Yomi, and initially claims that Hermit isn't one of Yomi, as she was still used to the presence of Chou Enshin. During the school festival, she wears the traditional Japanese outfit of a loincloth, shirt, and headband to play the large drum and getting a lot of attention. She tells Kenichi at this time that Yomi changed recently and that Hermit became a new member of Yomi.
After hearing that Miu had been kidnapped by Silkwat, she decided to help the Shinpaku Alliance locate their lost friend, wanting to repay them after Sakaki rescued her in an earlier encounter. Rachel sets up some equipment to increase the effectiveness of her presentation, but Renka Ma attributes her flashy display to Rachel's desire to attention. Castor then tells them where Miu may be found, allowing the alliance to inform Kenichi.
Once Jenazad is dead and Kenichi returns to Japan with Miu, Rachel and the other YOMI members disappear from school to tend to the needs of the syndicate as they plan for the future. After returning to Kōryō High, Rachel quickly becomes bored due to her lack of missions and decides to spend her free time with the members of the Shinpaku Alliance. She has Chikage Kushinada lead her to their headquarters, but Niijima and the Valkyries accuse her of being the enemy, and refuse to allow her inside. Rachel points out that since Hermit is allowed to hang around, they shouldn't have a problem with her joining in on the fun. The group initially refuses, but Kenichi vouches for her while expressing his gratitude for her help in rescuing Miu. She is shocked that he considers her a comrade, and seems happy when the group accepts her into the fold.
Shortly after, the three Yami disciples are then called away by their superiors, forcing Rachel to leave with Tanimoto and Chikage. After returning to the YOMI base, she is seen pondering Kenichi's words while getting dressed in her Lucha Libre outfit. She silently questions what he meant while wondering what YOMI is in comparison, but soon joins the other disciples at the meeting. Rachel asks Ryūto Asamiya for his opinion on the subject, but he dismisses her question, instead focusing on the strange killing intent in the air. The group is greeted by Mikumo Kushinada, who introduces them to unseen allies. Someone tosses a series of shuriken at them, but Rachel easily catches the one directed at her, threading her finger through the hole in its centre.
She is then called back with Hermit and Chikage as Mikumo pairs them with Berserker and Lugh as she sends them to kill Kenichi and his friends, which seems to please Rachel. She later arrives at the amusement park with the other YOMI members and later at night causes an explosion to find Renka and the two prepare to fight each other, both agreeing they need to settle the score with each other. There fight results in Rachel ripping Renka's swimsuit from her prompting Rachel to admit her pleasure from her embarrassment despite Rachel also losing some of her outfit. They both are embarrassed by Ukita seeing them and throw things on fire at him and they lock each other in a hold as he leaves.
They continue fighting till both nearly have no clothes left as Rachel holds her in a lock bragging how Lucha Libre is more beautiful than her Chinese Kempo. However, seeing no one else around to cover herself, Renka goes all out and breaks free and gains the advantage. However, Rachel also decides to go all out, emitting a dark aura rather than her cheerful self, realizing Rachel was holding back to use her flashy moves. As Rachel unleashes a brutal counter attack, Renka makes a comeback with her true strength, sending Rachel to the ground and her losing her mask stating she refuses to lose. However, Niijima, Thor and other Valkyries show up and the fighters are embarrassed they saw them naked, which has Renka angrily kick Niijima for not telling them they were there. Rachel feels ashamed she used non flashy moves and runs away.
Some time later, Rachel is present when some disciples from the weapon's team is introduced by Kajima and when Hyōgo attempts to mock them to test them, Rachel responds by trying to hurl him with a flip only for Hyōgo to stop her. She tries to kick him after mocking him for being weak only to be surprised he cut part of her clothes off in a flash and subdued her.
She was later seen with all the other Yomi members, including the armed disciples, as they prepare for battle. However, Sigmarigen taunts the unarmed division Yomi about their effectiveness in a real fight as Hyōgo tries to calm him down. Rachel answers back and makes fun of the weapon users and calls their weapons "toys", prompting Edeltraft's and Mildred's disciples, as well as Boris Ivanov and Chikage Kushinada, to join the argument. The fight is called off by Kajima, who later assembles all of them together to prepare for battle.
She was later seen with the rest of YOMI (minus Kajima) facing the Shinpaku Alliance. After Kenichi, Miu and Niijima escape, she and the other disciples charge the Shinpaku Alliance.
As the battle progresses, Hyōgo asks if the Yomi of the unarmed group to lend them a hand as they are just standing behind them with no intent to participate, as Rachel says they are soaking in the glory of the armed division. Edeltraft's disciple is about to land an attack on Ukita, which Rachel Stanley notices as she jumps into the fight. She appears to protect Ukita, pinning him between her legs and stopping the attack from Edeltraft's disciple, though she proceeds to throw Ukita into the ground afterwards.
As Chikage begins a ruthless assault on the alliance, Sigmarigen is impressed by Chikage's complete obedience to her master's orders but Rachel Stanley comments that something is different about her. She mentions that Chikage used to always struggle which brought about how people were charmed towards her, but that has now gone.
After Chikage's assault on the armed division's lack of honour and ganging up on the Shinpaku Alliance, Rachel and her brother ally with Shinpaku.
Once they start to overwhelm the weapons team Hyōgo starts to have them work together more effectively. Just then, two masters: Chin Sōgaku (crescent moon spade) and Ortal Sin (jamadhar) arrive and begin to put pressure on them. However, Ryūto, Renka, Koan Shokatsu and Genson Ryu, Renka's fellow disciples, also arrive and attack the enemy reinforcements. Once Ryūto tells them what to do, the Stanley siblings back up Ryūto against Chin.
They all defeat the masters as after the armed forces retreat, they celebrate their victory.
In the Epilogue, Rachel has pursued a career in Mask wrestling along side her master as she was seen gleefully enjoying the crowd with her master.
- vs 12 Dojo's (won)
- vs Underground fighters 14 match's (won)
- vs Renka Ma (undecided)
- vs Renka Ma round 2 (undecided, was losing)
- vs Hyōgo Itō (undecided)
- with Ethan vs wrestlers (won)
- with Ethan vs every opponent in the D of D Tournament (won)
- with Ethan vs Russian soldiers (Won Killed them)