The Price of Memories is the 2nd chapter in Tsubasa: Reservoir Chronicle.
In the country of Japan, there lives a strong ninja named Kurogane. He serves Tomoyo, the princess of the land. Though he is capable of defeating several warriors at once, he still desires to become the strongest warrior of all, no matter what the cost. Tomoyo acknowledges that in all of Japan, nobody can beat him, however, she believes he still needs to learn more in order to know the true meaning of strength. With her magic, she sends him to another dimension as well as casting a spell that will decrease his strength should he kill others recklessly. In the country of Celes, Fai emerges from a pool where the sleeping Ashura lies. He mentions that there is nothing left for him in this country, so it is time for him to leave. He wishes to be in a world without King Ashura in it. Before leaving, he asks his creation, Chii, to let him know when Ashura awakens. He then transforms her into a barrier over the pool, and then leaves to go to the "Witch's origin."
In a more modern-seeming world, the witch Yuuko explains to Syaoran that if Sakura's scattered memories are not retrieved, she will die. Syaoran declares that he is willing to do anything to get them back. Subsequently, Kurogane and Fai appear, each with their own request: Kurogane to return to his own world, Fai to avoid his own world. Yuuko announces that essentially, all their three wishes are the same, but in order to fulfill them, each must give up something precious to them as payment. From Kurogane, she takes his sword; from Fai, he takes his tattoo; and from Syaoran, she demands that he give up his relationship with Sakura. Though her memories may be returned, they will never again return to what they once had in the past. He agrees, and she gives them Mokona, which can lead them through their journey to the other worlds.