Sakura is the princess of a country called Clow, and lived in the castle there with her father, Clow Reed, her brother Toya, and the high priest, Yukito. In the desert that surrounded the town and castle were ruins, so old that no one in Clow knew their function anymore. Heading an excavation was the archaeologist Fujitaka Kinomoto. This archaeologist adopted a young orphan who couldn't even remember his own name and called him Syaoran.
Sakura met Syaoran when Fujitaka reported some of his findings to the king, and the two became fast friends. Sakura slowly began to help Syaoran become a happy, relatively normal little boy, and the children soon began to have feelings for one another. She gave him her birthday, April 1st, when she found out he didn't remember his. Sakura's and Syaoran's fathers both died when they were relatively young, leaving Toya to become king and Syaoran to take over his father's excavation.
Things were relatively normal until, the day before Sakura plans to tell Syaoran her feelings, she hears a bell-like sound from the ruins. She goes into a trance and sees an odd vision of fragmented images, one a picture of wings. The next day, Syaoran finds the same symbol at the bottom of the ruins, and when Sakura arrives to have lunch with him, she tells him she saw the same thing yesterday. She goes into another trance and kneels on the symbol, which causes light to shine from the wings.
Odd soldiers with a bat-like symbol on their uniforms appear and attack the people above ground while, under the ruins, Sakura floats into the air with the symbol behind her. Wings, in the same style as the mural, appear from her back, and Sakura falls. Syaoran catches her, and the wings shatter into feathers and disapate while Sakura slowly becomes colder. Syaoran brings Sakura to Yukito, who tells Syaoran that those feathers were Sakura's soul and memories, and that if no one gets them back, she will die. Yukito sends Syaoran and Sakura to Tokyo, where he says "The Witch of the Dimensions" will help.
Her name is Yuuko, and she confirms what Yukito said: without her feathers, Sakura will die. In addition, they have been scattered across the worlds. Two more people arrive, Fai, who wants to leave his world behind, and Kurogane, who wants to return to his world. Yuuko says that it will be a high price for all of them, but that together, they can pay it. Kurogane must hand over his sword, Fai the tattoo that controls his magic, and as for Syaoran… Sakura will never remember their childhood together, even if she regains all of her feathers. They are given Mokona, a creature who can travel to different worlds, but cannot control which ones, and who can sense Sakura's feathers.
So they travel from world to world, and Sakura slowly regains her feathers, and with them, her memories. All is (relatively) well once again, until they come to an alternate Tokyo. Here, it is revealed that the Syaoran who Sakura knew for so long was only a clone. The real Syaoran was imprisoned by Fay Wong Reed. Before this, though, he gave the clone his eye and thus half of his heart. This way, the clone wouldn't be a mindless killing machine, and he could watch what happened through the clone's eye. The real Syaoran had hoped his clone would "grow" a heart, but when the real Syaoran awakened and hunted the clone down to take back his eye and half of his heart, the clone lost all feeling and attacked Fai, ripping out his eye and consuming it to take half of his magic. The real Syaoran attacked him and tried to kill him, but failed when Sakura, who was trapped in a sort of shell, screamed for him to stop. The real Syaoran hesitated, leaving an opening for the clone to stab him in the leg. He then took one of Sakura's feathers, leaving her dazed, and left. He'd also managed to destroy the world's only water supply.
Sakura was understandably shaken and hurt by this. The group decided to ask Yuuko to replace the water supply that the clone had destroyed. They travel to the next world, called Infinity, and fight in a tournament. This tournament is called chess, but the only real similarities are the white and black costumes and the fact that the "pieces" (Kurogane, Syaoran and Fai) are controlled by a "master" (Sakura). Sakura tells everyone this is so they can use the prize money to help keep restoring the world that the clone destroyed. The truth is, however, that Sakura wants the other part of the prize - a robot (Freya from Chobits) who can take only one person to another world only once. Sakura has seen a vision of Fay stabbing Syaoran, then going insane and killing the group. After that, he would commit suicide, and she wants to prevent it. She would use the robot to travel to another world to not only find the clone, but to help change the future. In order to do this, Sakura gives up her exceptional good luck to Yuuko as fair payment. It is revealed that Fay is under a curse that forces him to kill anyone who is stronger than him. The only reason that Fay didn't kill Yuuko was because she was in a different dimension when he met her to prevent the curse from being activated- the one there was a sort of hologram, which is hinted at by the fact that though it was raining, she was the only one not getting wet. When Sakura receives two feathers in Infinity, she becomes stronger than Fay. Because of this, Fay stabs Sakura in the stomach, and Sakura's wish keeps him from killing Syaoran.
Sakura had asked Yuuko to transport her soul to a dream world, thus preventing Fay from going insane, and to transport her body to Celes. There is a feather in each of these worlds, apparently, which is why she chose them. It's successful, up until the robot wraps her arms around the Princess to transport her. When she wakes up, she's in the infirmary, being treated for massive blood loss among other things. And her plan has failed.