The Power of Belief is the 225th chapter in Tsubasa: Reservior Chronicles.
The real Syoaran and Sakura are together, reflecting on the memories and the promise they have made. The both of them vow to continue to protect and each other and the people they love. And if the time comes that the two of them will be separated, they will continue to search for each other again and again.
Syoaran's father entrusts his powerful sword to his son. He also entrusts him with the "name he bears" which is Syoaran. All that remains to happen is for a letter to reach Sakura's relatives, so that they may send a person to them for the price of a staff (the one that Sakura received in her dream) and a container.
Everything is going according to Sakura's dream. Syaoran's family was entrusted with "the container" in a will to his protection. The will that he is referring to is the one of a wizard with blood relations to the Li family, one named Clow Reed.
With the power that he has been granted, Syaoran plans to find a way out of their endless loop of life. Then they both become encased on the container The both of them will not allow their children and future selves to have the life depicted in the dream. They will wait for the day the both of them can meet again.
The Sakura and Syoaran that Fai, Kurogane, and Mokana have been traveling with are the clones that Clow Reed created.