Artoria Pendragon, once known as King Arthur and the Once and Future King, rests in Avalon, the Everdistant Utopia, after her death. Avalon is the Land of the Fairies and exists outside of time and space, a reflection of her dream of a perfect kingdom. As a reward for her life of fighting and hard work, Avalon offers to put her into an eternal sleep filled with good dreams, but she declines. Shortly before her death, she was summoned into modern Fuyuki, Japan to be Shirou Emiya's Saber Servant for the Fifth Holy Grail War. Though their time together was short, they lived and fought side by side and fell in love. Though the action separated them, they had to destroy the corrupted Holy Grail before it could destroy humanity. Now in Avalon, she remembers a prophecy Merlin made, "One must keep waiting, and another must keep pursuing." So she stays awake and waits, having faith that one day, after fulfilling his ideal of being a Hero of Justice, Shirou will make it to Avalon and find her, no matter how many centuries it takes.
Out of nowhere, Artoria hears a male voice scream, "Asia!". At first, she thinks it is Shirou, but then realizes it doesn't sound like him. She gets up from the grass. She wears an elegant white dress and has her hair down. She is in a beautiful sea of grass between mountains and forests, a completely natural landscape. The Fairies had not visited her since she arrived and only those who are deemed worthy can enter here. As she wonders who said that, the voice screams in Japanese (which she is able to understand) to someone to let go of him and that he needs to save his friend Asia. She then speculates that the speaker is someone who resonates with her existence for her to be able to hear him here. The voice begs someone, anyone, to save her. Artoria decides she can't face Shirou if she doesn't at least try to help.
Artoria weighs her options since she can't exactly leave Avalon. The only thing she can think of is her old contract with the World to be summoned as a Servant to seek the Holy Grail. She severed that contract when she destroyed the Grail, but there are infinite universes and other versions of herself who may still hold that contract. Talking out loud, but aware the voice will likely not hear her, she says for this to work, he needs to be in a world with a Holy Grail and be near a magic circle. If he is, then she will help him. She concentrates and her attire changes back to her blue dress with armor and her hair in a bun. Now, all she can do is wait and pray this works.
Eventually, Artoria feels herself leaving Avalon, and sees a sea of stimuli no human mind is meant to perceive. She knows that it worked and she has been summoned. She fondly tells Shirou that she's just going to pass the time until he arrives and she'll be back before he gets home. When she materializes in a new world, she can tell she's in the middle of a conflict and she is surrounded. She looks around, then says, "I ask you..."
