Tsubasa: RESERVoir CHRoNiCLE

After the Clone left, the water has drained from the Municipal building and Fai is dying due to the loss of his eye that the clone ate. Subaru wishes to have the water restored, while Kurogane wishes to save Fai's life. Fai is fed with vampire blood and becomes a vampire, thus saving his life, and the water is restored. The price of the water, however, is that Sakura must seek out a treasure somewhere in Tokyo.