The Beginning of the World is the 1st chapter in Tsubasa: Reservoir Chronicle.
Trapped inside a glass tube, unable to touch each other, glancing at each other, pain and tears rolling from their eyes. Syaoran bangs on the glass, while feathers sprout of her back, and she's taken away as Syaoran yells at her, "Sakura!"
In Clow Kingdom, a young archeologist had just arrived home after a long time researching the Ruins of the west. He greets his father's photograph, saying that his theories were correct. Someone else arrives to visit him. It is Sakura, who jumps and hugs Syaoran excitedly, asking him if he's ok. He replies he's okay, calling her Princess, though she doesn't want to be addressed in a formal manner, so he ends up calling her Sakura with a little difficulty. She welcomes him back, knowing this because the team came back to the Castle. She says that her brother is upset whenever she comes to visit him, but he is her dearest childhood friend after all.
These childhood friends, who met several years ago, began to reminisce about the past -- Syaoran and his father, a renowned archeologist, arriving in the Kingdom; the death of Syaoran's father (who is Fujitaka from Card Captor Sakura too); Syaoran refusing to live amongst the royal family, and working as an archeologist himself and being busy much of the time, leaving Sakura lonely. She knows that this is important to him, though she's left to wonder sometimes "What is Syaoran doing at this moment? Is he thinking about me?", to which he replies that he does as well.
Just then, as Sakura finally finds the courage to admit her feelings and say that she loves him, a bell tolls and Sakura knows that it's her dinner time, so she has to go. He wants to walk her home, though all people in Clow are nice people and there is no need. But before leaving, she says to him that she'll definetely say those words and he must wait for them. As she leaves, the townspeople are just as nice and welcoming as Sakura said earlier, they seem to have a deep respect and affection towards her.
Syaoran wonders to his father if having these feelings is alright to him, even if they're childhood friends after all.
In the castle, Sakura tries to sneak behind her brother Touya but he sees her anyway. He's upset that she went to see Syaoran, calling him a brat. Yukito, the priest, appears and tells Touya to stop. Yukito tells Sakura that the excavation has progressed a lot, though not enough, meaning that Syaoran will still have a lot of work to do in the ruins, so he won't have time for Sakura. She tries to shake off the subject saying that Syaoran will be happy for it, and runs off. Yukito tells Touya to stop that attitude with Syaoran for it only makes Sakura sad. They agree that he's the one for her.
The Priest also saw that they will face terrible danger for the Princess' unknown powers, one that can change the world.
Sakura looks out the balcony, to the ruins. She's thinking of telling Syaoran tomorrow that she likes him. But she hears a strange sound, the sound of bells, and they are calling her. She floats out of the castle and has several visions of things that are about to happen.
Next day, Syaoran goes deeper into the excavation. He finds an odd symbol that is not of this country, and that he's never seen before. Suddenly, Sakura appears to bring him some lunch, but Syaoran worries that something could happen to her. They're inside the underground passage, and they can't go any further, nor they can drill through the rock with the mark. Sakura touches the mark while undergoing some state of trance. The ground opens, and Syaoran is unable to do anything.
Yukito and Touya feel an earthquake, but Yukito says it wasn't an earthquake. Then people in black with some bat marks come out and fight them. Sakura is now up high the ground, and some black wings appear out of her back. Syaoran tries climbing up to her.
Someone else is watching them, saying that the feathers will show him the way.
Sakura seems to be pushed into the wall, just in time, Syaoran grabs her out. She falls to the ground, saved by Syaoran, while the ruins collapse. A girl remarks, "It failed, didn't it?"
The same man from before still watches, saying that everything will start now, and he will have the power to reach another dimension.
Syaoran manages to get out, only to see that there was a great battle, leaving King Touya badly injured, as the swords had poison. Yukito reads Syaoran's mind and knows that the Princess' feathers are now scattered, those feathers represent her memories, and they are all gone. Yukito sends Syaoran off, to another world, to find the person with his same power of the moon, who is the Witch of Dimensions.
They arrive and find the mysterious woman. Syaoran yells for her to help Sakura.