Fay D. Flourite (ファイ・D・フローライト Fay D. Furōraito?, also romanized as Fai D. Flowright) is a powerful magician from the country of Celes. He travels to Yūko on his own accord after sealing King Ashura of Celes and having his creation, Chī, act as a barrier to alert Fay if Ashura awakens. He wishes never to return to Celes and have the ability to run away through dimensions if Ashura does awaken, so he gives up a tattoo on his back in order to have use of Mokona. Fay is a very enigmatic person. He appears to be happy-go-lucky and good-natured, and acts very carefree. He often teases Kurogane, calling him ridiculous nicknames such as "Kuro-rin", "Kuro-tan" and, in the English version, "Kurgy". Kurogane questions this nature, sensing that it is just a false persona to hide that he is emotionally distant, and Fay usually gives very dark and enigmatic answers if asked about it. Fay doesn't bother to fight very hard for his life, and will only do so if someone he cares for is in danger, which Kurogane notes to be Syaoran and Sakura, as the group bonds. He is voiced by Daisuke Namikawa in the anime adaptation, and by Vic Mignogna in the English adaptation.
Fay's real name is "Yūi", and he is born with his identical twin brother, Fay, in Valeria Country[2] The birth of twins to the second prince of the country is a bad omen, which leads to the death of their father, the suicide of their mother, and many misfortunes upon the country. Fearing the combined magical power of the twins, the king imprisons them within a tower where sinners are kept, where magic is ineffective and time flows differently. Fay is imprisoned atop the tower, and Yūi is confined at the base of the tower. Bodies eventually begin to fill the base of the tower, and Yūi attempts to climb towards his brother. The King, insane, eventually jumps into the tower, revealing that he has killed everyone in the country, and then kills himself to remind them that they are the cause of everything.
Eventually, Fei Wang Reed appears from another world, and offers to free one of them. Fay chooses to save Yūi, resulting in Fay being thrown from the tower to his death, though Fei Wang tampers with Yūi's memory to make him think that he chose his own life over Fay. Promising to return Fay to life if Fay becomes his pawn, he bestows two curses upon Yūi, one of which is removed from his memory. The curses are to kill whoever is a stronger magician than him, and another curse will use his magic to collapse the world around them. He tells him about the journey he will have with Sakura. He is soon found by Ashura, who takes in Yūi, having adopted the name Fay. Ashura also bestows upon him the surname Fluorite, which is a precious stone found in Celes. Fay is given one of Sakura's feathers to preserve his dead brother's body. Ashura tutors him in magic and comforts him, and Fay discovers another two of Sakura's feathers; one he must give to Sakura when he first meets her, to prevent her death, and the other is used to create Chī, whose appearance he bases on his late mother. He eventually learns that Ashura's purpose is to have him kill anyone who threatens the country, which means to kill Ashura himself, as Ashura kills people in order to make his magic stronger. Instead of fulfilling that role, he seals Ashura with a sleep spell.
Fay has natural magic abilities that grow stronger every time he uses them, though he notes that they are only good for destruction. The source of Fay's magical powers is the blue color of his eyes, which also greatly increases his lifespan. His left eye increases his powers on usage while his right eye decreases his powers, as noted by Seishirō and Fūma in Nihon. Since his powers are directly connected to his eyeballs, a loss of vision leads directly to a loss of magic, and a total loss of magic would lead to his death. Ashura, wishing Fay to kill him, when he has become stronger than Fay, places a tattoo on Fay's back to keep him from growing stronger than himself. Once the tattoo is given to Yūko, he refuses to use his magic. His powers are effectively halved when Syaoran consumes his left eye, and they continue to diminish afterward. He is forced by Kurogane to become a vampire to save his life. He gains regeneration and no longer has to rely on his magic to survive, though he has to regularly drink Kurogane's blood. Kurogane sacrifices an arm to save Fay from his last curse. He later gives up the rest of his magic in order to pay a "price" for Yūko (to restore Kurogane's lost arm with a mechanical one), which leaves him with a permanently gold vampiric eye. Later he recovers his lost left eye, which Syaoran had been using. The magic, which had been increasing every time the clone used it, is strong enough to restore Fay's lost eye. His magic is returned to him and he is able to use it to its full potential.