ok , just read the translation, and it's said that
Yuuko: There's one more thing. If you get his stolen left eye back, Fai's magic will also return. If you get his eye back, your role as prey will also end., so Fai won't recover his eye on its own, but SOMEONE has to get it back from C!Syaoran if he wants back to normal.....owww...vampire forever until meeting C!Syaoran...