The Truth Within the Ruins is chapter 201 of Tsubasa Reservoir Chronicles.
Fei Wang Reed was about to grant Syaoran's wish but Yuko overthrew Fei Wang's magic circle. Yuko has the power to grant it however it would be a grave sin. By turning the hands of time, Syaoran may be able to change the course of the princess' future. However the future of all involved would also be changed in the process. Particularly, the futures of those who knew of the seal upon the princess and it will be Syaoran who will bear the responsibility for any consequences that may follow as a result. Though having held the responsibilities, Syaoran may never be at the princess' side. Syaoran will lose his freedom and his life will be in grave danger, and he has nothing to do but to watch. In order to fill the void left by the "relationships" that Syaoran has paid for as his price, Watanuki has been created to take his place.