Miyu is the complete Holy Grail from the world in which the Class Cards originated. Her real name is Miyu Sakatsuki (朔月 美遊, Sakatsuki Miyu?) of the Sakatsuki family, the hidden descendant of the Child of God (神稚児, Kami Chigo?). She was raised carefully within the Sakatsuki residence and was given limited education, isolated from other children and relied only to her mother.
When Julian Ainsworth unleashed the black shadow in Fuyuki in the Fourth Holy Grail War, Miyu responded to the cries of the people and nullified the shadows. Shirou Emiya found her location when she activated the wish and saved her from a collapsing roof. Shirou brought Miyu back to Kiritsugu Emiya, who was thrilled to learn that she is the tool that he was looking for. Kiritsugu, Shirou and Miyu settled in the Emiya residence. Kiritsugu was researching on how to use Miyu before she loses her ability and treated Miyu coldly like a tool. However Miyu was attached to Shirou which caused Shirou to be emotionally conflicted.
After Kiritsugu's death, Shirou couldn't treat her like a tool or even raise her like a normal child, so she was confined within the Emiya residence. Shirou gave her textbooks for her education, but it was the knowledge that didn't hurt her and for non-practical use. When Miyu became ten years old, she had developed more human expressions. When Shirou reminisces Kiritsugu's last moments, Miyu unknowingly activated her wish that Shirou and Miyu become true siblings. Shirou at that moment decided to treat her more like a sister and to take her outside to see the ocean. Shirou took Miyu back to the Sakatsuki residence and tried to explain to her about her family and his intentions on saving her. Shirou's explanation was interrupted by Julian, when he accused Shirou to be a thief. Shirou tried to tell Miyu to run but she didn't know where to run and Julian kidnaps her.
After Shirou won the Fifth Ainsworth Holy Grail War, she is teleported to another Parallel world through Shirou's wish upon the Holy Grail. However, since Shirou was fighting Angelica in his Reality Marble, he was not taken with her with everything else in the cavern such as the Class Cards and the Holy Grail Ritual circle. Later upon arriving in Illya's world, she was taken in by Luvia in her search to rival Illya and Rin's partnership.
Miyu is a young girl with black hair tied in low pigtails, and golden-brown eyes. As a normal girl, she wears the standard uniform of her elementary school with long black knee socks, and other outfits usually picked by Luvia. When she becomes a magical girl with Kaleidostick Magical Sapphire she wears a cute blue and black outfit with a white cape and boots. She also wears a strap on her left leg where she keeps the Class Cards.
When she Installs the Saber Card, she wears an outfit that resembles the original Saber without the chest armor. When she Installs Rider, she wears the same outfit as the original counterpart. When installing the Archer Card containing Gilgamesh, she wears a armor and cape that resembles the original wearer except with the abdomen exposed.
When being held captive by the Ainsworth, she wears a revealing black dress with her hair tied to the side by a blue flower.
Before and during the Fifth Ainsworth Holy Grail War, she normally wears a kimono (a normal one and cooking apron). Her eyes were also notably red with a golden shine instead of golden-brown until she wished to be a real sister to Shirou, giving her Shirou's eye colour as proof of being biological siblings. When being used as a Holy Grail and granting Shirou's wish, she wears a black babydoll dress with three bottom ends that can shape the entire outfit like a cross.
When she wears a kimono, Illya points how Miyu looks like a natural Japanese beauty.
Originally, Miyu has a mature, dutiful, and rather unfriendly personality. She takes her duties as a Magical Girl very seriously and is initially dismissive of Illya's abilities. She is very knowledgeable that she tends to view everything more logically while explaining or exploiting the hard facts behind it, not understanding the emotions surrounding them. This side of her expresses how she lacks imagination and hints a sense of loss in child innocence. Despite this, she is shown to have vulnerable sides such being embarrass and being timid towards those who conveys acts of deep kindness and other possible overwhelming emotions like obsession.
When she opens up to those she becomes close to (mainly Illya), she exhibits the capacity to deeply care and is very dedicated towards them. This creates two sides to her personality where she can very affectionate and devoted to someone she cares for, but extremely cold and dismissive towards anyone else.
It is revealed in the past that she was originally stoic if not emotionless due to her duties of being the Holy Grail but showed sense of attachment. Her interactions with Emiya Shirou, who she eventually calls her brother, soon brought more color and emotions to her world while also bringing deep guilt and burden in her heart. This, along with the Ainsworth's treatment towards her, unveils the reason behind the personality she had when she was first introduced. Because of her upbringings, the guilt, burden, and turmoil within herself brought her great despair that she almost gave up on the idea of hope, but after Illya and her allies/friends saved her, she begins to show resolve. Like Illya, Miyu also seeks a path where everyone can be saved.
She comes to value Illya's friendship greatly and is highly protective of her. This dedications goes as far as willing to risk her life for the sake of their friendship. She shows another side of her personality when she is around her brother, where she behaves like the young girl she actually is. These behaviours include wanting to be spoiled, like to wear animal onsies, and throwing a childish temper.
After reuniting with her brother and having the entire group stay in the Emiya residence, it was shown that she likes animal-themed pajamas; and acts rather spoiled in front of her brother.
Fate/kaleid liner PRISMA☆ILLYA
Miyu takes on the Edelfelt name after being taken in by Luvia. She lives in Luvia's mansion and acts as her maid to earn her keep. She uses Ruby's sister Kaleidostick, Sapphire, in order to transform, and she initially has a much better understanding of her abilities than Illya. She takes her role very seriously and treats Illya as a bothersome rival, though they eventually become close friends. She later gains the ability to use the Saber class card to embody the Heroic Spirit after seeing Illya perform it.
Fate/kaleid liner PRISMA☆ILLYA 2wei!
Miyu continues to fight as a Magical Girl, dealing with the mysterious 8th Class Card. After dealing with Illya's split personality, Kuro, Miyu and co. fight the Enforcer, Bazett. They defeated Bazett and cooperated with her to capture the 8th Card. After spending some happy summertime days with her friends, Miyu and the others are alerted by Rin and Luvia to the eighth card's location. During these days, Miyu also expresses some hesitation about revealing her past to the others.
Upon arriving at the eighth's card location, it is revealed that the 8th Card had come from another Holy Grail ritual. Confronting the newly summoned Archer Servant (Gilgamesh), Illya inadvertently splits the Servant into two and it gains a physical body, in the form of Child Gilgamesh. After dressing himself, Gilgamesh revealed that Miyu is technically a princess who comes from a parallel world. As he is explaining this, Gilgamesh's main body tries to absorbed Miyu to power itself up. However, she is saved by Illya using the combined power of the Ruby and Sapphire sticks with help from Chloe and the others.
Fate/kaleid liner PRISMA☆ILLYA 3rei!!
In Fate/kaleid liner PRISMA☆ILLYA 3rei!!, Miyu is a captive for the first half of the series. After Miyu was taken back to her own world, she was kept locked up and held captive inside the Ainsworth Castle where Julian Ainsworth possessed by Darius Ainsworth threatened her into giving up her blood to carry out a magic ritual that carves out his own heroic epic onto stone tablets by threatening to kill Miyu's older brother (the Emiya Shirou of her world). Over this period, Miyu bonds with Erika Ainsworth, who she sympathizes with and tells Erika all about Illya.
During Illya's rescue attempt, Miyu is convinced again by Julian that her world is dying and that the only way she can save it is by forfeiting her own life. While Julian (still possessed by Darius) tries to convince Illya to make a choice between saving the world or saving Miyu, Miyu's body becomes wrapped by invisible chains. However, Illya's declaration of choosing to save both and to use the Holy Grail to wish for everyone's happiness makes Miyu so happy, she breaks free of them and reunites with Illya, Sapphire and the others.
After Miyu is rescued from Darius, the group reconvenes at the Emiya's old house where Shirou reveals his and Miyu's origins. In his story, it is revealed that Miyu's original name was Miyu Sakatsuki. She was a "Child of God", a child from an occult religion that believes children to be the closest to God and spirits. In a past age of a high death rate of child birth, the religion worshiped children below 6 years old as entities between gods and humans, and as a child of the last remnant of this religion this granted her wish-granting powers, not unlike the Holy Grail. Kiritsugu and Shirou found her five years ago in an incident that almost destroyed Fuyuki in an enormous black shadow, and witnessed Miyu dispel it. Kiritsugu took her, wishing to utilize her wish-granting power to save the world.
Kiritsugu asked Shirou to use Miyu to grant his wish of world salvation, but Shirou couldn't do it because Miyu became more human each day and he began to care for her as a person instead of a tool. Kiritsugu died some time later, and Shirou continued to taking care of Miyu. At this point, Shirou and Miyu became close with each other. After Shirou explained why people wish upon the stars, Miyu unknowingly used her power to wish for her and Shirou to become real siblings, indicated by the change of eye colour from her previous red to the same amber eyes as Shirou.
- Main article: Miyu Edelfelt (Servant)
As a normal elementary school student, Miyu possesses knowledge and athletic skills that make her a genius even among adults.
As a Magical Girl, Miyu is able to utilize the Mystic Code Kaleidostick, Magical Sapphire, to tap into mana from parallel worlds and gains virtually unlimited magical energy. She also can utilize Class Cards; Including them to provide her Heroic Spirit's Noble Phantasm and Installing them to gains Heroic Spirit's abilities.
As the Child of God, she possess the capacity into becoming a complete Holy Grail unlike Illya or Chloe who are only Lesser Grails. However, this power seems to have disappeared after she turned 10 years old. It is shown that certain rituals/preparations are required for her to function as a Holy Grail that can grant wishes. Like in the original Fate/Stay Night, one of those rituals is the Holy Grail War. In accordance to certain wishes, Miyu could end up forfeiting her life to grant those wishes.