Fate/kaleid liner Prisma Illya

Illya has been chosen by the Kaleidostick Ruby to become the new magical girl.

A challenger appears, just when Illya is having trouble collecting the Rider card under Rin's instructions.

A mysterious transfer student, Miyu Edelfelt, has joined Illya's class. Is she friend or rival?

Illya and her friends have been defeated by Caster. They must figure out how to improve their teamwork in order to win the rematch.

There is no time to celebrate their hard-won victory, as Saber card suddenly appears to strike down Rin and Luvia. Faced with their strongest opponent yet, which option will Illya and Miyu choose?

Illya calls upon the power of the Archer card to defeat Saber.

With the ley lines failing to recover despite the cards being retrieved, Rin and Luvia bring Illya and Miyu with them to help seal the lines. However, something goes wrong, leading Illya to become split into two separate people.

Illya finds herself targeted by her dark clone, Kuro Illya, whose creation has resulted in Illya's power becoming weaker. Rin and the others attempt to lure Kuro into a trap, but her ability to read everyone's moves leaves them at a disadvantage. However, Illya manages to draw Kuro into a bog, allowing her to be captured.

After failing to get any information from Kuro, Rin places a seal on her that would cause her pain if anything happens to Illya. When Kuro escapes, Illya has to take drastic measures to keep her from making moves on Shirou. The next day, Kuro causes more problems for Illya when she starts randomly kissing other girls at school to replenish mana. When the two are spotted together by her classmates, Kuro decides to pose as Illya's cousin.

Kuro transfers into Illya's class, much to Illya's dismay, and is immediately thrust into a dodgeball match against the classmates she kissed the other day. Feeling her school life is at risk, Illya steps in to challenge Kuro one-on-one, with both sides bringing out their full magical power. Kuro lands a critical hit on Illya's face, but due to their shared pain they both pass out, ending the match in a draw. Whilst recovering, Kuro suspects the school nurse knows more about her existence than she lets on. As Shirou comes to pick up Illya, Miyu is a little perturbed by Kuro's words that she shouldn't stay too close to Illya, lest she find out things she has been keeping secret.

After Illya inadvertently blows up her house's bathroom wall, her family comes over to Luvia's house to use her bathroom, where Kuro causes more trouble for Illya. Later, as Rin and Luvia ask Illya about how she used the Archer Card in the manner she did, Illya's statement of wanting to return to a normal life angers Kuro, who reveals she herself possesses the Archer Card and escapes. The next day, Miyu is summoned by Kuro, who claims Illya's wish of a normal life excludes Miyu and the other people she had met as well too. However, Miyu has faith in her friendship with Illya and uses the Saber Card to stand up against Kuro.

Miyu and Kuro have an intense battle before Illya arrives to try and stop them, apologising for the words she said before. When Irisviel suddenly arrives to pick Illya up, Kuro tries to attack her, but she stops her with her own magic. Irisviel reveals Kuro was sealed away so that Illya can become the Holy Grail, with Kuro becoming upset when she learns the Holy Grail War no longer takes place, feeling she has no place to belong. She ends up overusing her mana and starts to disappear, but Illya gives her some of her own mana so that she can last longer. Told by Illya to make her own wish come true, Kuro wishes to have a family, allowing her to come back into existence as a proper member of Illya's family.

As Illya and her friends prepare for a trip to the beach, Mimi stumbles across Illya and Kuro doing their 'mana transfer'. Afterwards, Miyu comes over to Illya's house for a sleepover, where she acts bashful around Shirou.

Illya and her friends arrive at the beach alongside Shirou and his friend Issei Ryuudou. Whilst enjoying the beach, Miyu tells about how she has a brother, who Shirou resembles, before the girls come across Bazett, who is working part-time jobs to pay off her debts. Later, as everyone has a party to celebrate Illya, Miyu, and Kuro's birthdays, the celebrations are interrupted by some noisy construction from Rin and Luvia, who are attempting to dig for the eighth card, with Illya soon finding herself in the middle of an outrageous feud. Things become more troublesome when Ruby tries to inject Shirou with a love potion, though Sapphie soon sorts things out by erasing everyone's memories.

Plagued by thoughts of lewdness surrounding Illya and Kuro, Mimi starts putting her thoughts down into story, which soon turns into a gender-swapped boy's love story. This soon catches the attention of her classmate Suzuka Kurihara and her sister, who decide to use her story for a yaoi doujin. Concerned about Mimi's gradual transformation into a fujoshi, Suzuka asks Illya, Miyu, and Kuro for their help. Despite not being fond of Mimi's fascination with BL, Illya learns that it doesn't mean they can't still be friends.

Illya receives tickets to a theme park from Luvia and decides to go with her friends. When they lose track of Irisviel, who gets swept into a special event, they come across Caren, who agrees to be their substitute guardian. Later, Illya discovers the charm on her bracelet has gone missing, so Miyu decides to help her search for it. Taking some advice from Caren, Miyu manages to deduce the charm's location and find it before closing time. Afterwards, Kuro becomes curious about the relationship between Irisviel and Caren.

The girls attend the local summer festival, where Illya shows Miyu how to enjoy herself. Later, Rin and Luvia get into mischief in front of Shiro, while Illya uses her transformation to escape a wardrobe malfunction. Meanwhile, Kuro becomes aware that Miyu is hiding some kind of secret from Illya.

Having completed reconstruction of her mansion, Luvia invites everyone over for a house party, after which the girls discuss their plan to obtain the eighth card. As the girls prepare for what could be their final mission, Kuro questions Irisviel over how the cards are related to the Holy Grail War, which involved only seven classes. Ruling out the possibility of Irisviel being involved, Kuro suggests that they question Miyu, but Illya feels it is best to focus on the task at hand and find the answer themselves.

The girls learn that the crater created in the mountain during their previous battle has mysteriously disappeared. While investigating the scene, they are suddenly confronted by two new adversaries who overwhelm them and kidnap Miyu. As Illya tries to chase after her, she finds herself in parallel world covered in snow, where she meets a peculiar girl known only as Tanaka. Despite seemingly having no other memories, Tanaka is somehow able to tell Illya that Miyu has been kidnapped by the Ainsworth Family.

Illya and Tanaka are attacked by one of Miyu's kidnappers, Beatrice Flowerchild, before she is suddenly called away. As Tanaka explains that the only thing she remembers is her duty to eliminate the Ainsworth family, she and Illya come across a ramen shop, where the owner explains that a gas explosion caused the crater. When they are suddenly faced with a hefty bill, they are bailed out by the Heroic Spirit Illya previously faced, Gilgamesh, who helps lead them to the Ainsworth's castle in the center of the crater. Making their way inside the castle, they come across a prison cell containing Miyu's older brother, who urges them to save Miyu. Just then, they are confronted by the other of Miyu's kidnappers, Angelica.

Gilgamesh steps up to face against Angelica while Illya and Tanaka go off in search for Miyu, only to come up against Beatrice again. As Tanaka takes on brutal attacks from Beatrice, Illya manages to find Ruby among a pile of weapons, transforming once again and installing the Caster card to fight against Beatrice's Berserker. After Tanaka takes on a full blast from Beatrice, still managing to survive, Gilgamesh helps her and Illya make a retreat. Just as Beatrice and Angelica catch up to them, they are called off by the head of the Ainsworth family, Darius Ainsworth, while Kuro and Bazett also arrive in the parallel world.

Kuro brings Illya and the others to the school, which she and Bazett had been using as a base. Kuro then explains their situation while Bazett gives Illya the Saber, Rider, and Lancer cards. As Gilgamesh explains to Bazett what the cards are, Kuro, notices Illya feeling sorry for herself, confronts her in a battle, forcing her to use the cards she received from Bazett to defend herself. During the battle, Kuro informs Illya that her fears of being in an unknown world are the same feelings Miyu kept to herself all the while. Winning the battle with the Saber card, Illya comes to understand what Kuro was teaching her.

Illya helps out a girl named Erica after she gets stuck on the school's walls and wets herself. As the girls take a bath together, they learn that Tanaka had lost her memories just before meeting Illya. Afterwards, as Sapphire manages to get in contact with Ruby, Erica is picked up by her father, who turns out to be Darius himself.

Darius traps Illya inside an ice barrier Noble Phantasm which slowly cuts off her oxygen supply. Tanaka manages to break through the barrier, allowing the others to come to Illya's aid, but they are all helpless to fight against Darius. After taking an interest in Tanaka's abilities, Darius takes his leave, with Erica leaving some disturbing words for Illya. As Illya and the others try to figure out their next move, Darius performs a painful ritual with Miyu. The next day, Kuro discovers that Illya has disappeared, leaving her Class Cards behind.