I got this from Animenewsnetwork.com:

Plot Summary: Sakura, a princess from the Clow Kingdom, lost her memory due to a strange incident that happened within an archeological dig in her home country. In order to regain her memory, Yukito, the Kingdom's mage, sent her childhood best friend, Syaoran, to seek help from the witch, Yuuko. Yuuko tells Syaoran that he has to travel from one alternate reality to another to collect fragments of Sakura's memory. However, even if Sakura regains her memory, she will have no recollection of Syaoran. Travelling together with them is a Kurogane, warrior who was exiled from his country, and Fye, a mage who wants to move from one reality to another in order to escape from his King. With the help of a magical creature, Mokona, they set off on an exciting journey through time and space.