Fye D. Flowright, originally named Yuui, was born alongside his twin brother Fai in Valeria Country. Their birth triggered a catastrophic omen, resulting in their father's death and mother's suicide. Blamed for ensuing national disasters, the twins were imprisoned in a deep valley tower—Fai at the top, Yuui at the base. The Valerian king, descending into madness, slaughtered the population before taking his own life before Yuui, leaving the twins as sole survivors condemned to eternal isolation. Fei Wong Reed appeared, offering freedom to one twin. Fai chose to save Yuui, sacrificing himself by being thrown from the tower. Fei Wong altered Yuui's memories, making him falsely believe he had prioritized his own survival. He then cursed Yuui: one curse compelled him to kill any stronger magician, while another caused dimensional collapse. Fei Wong instructed Yuui to await rescue, protect Princess Sakura, eliminate obstacles, and use magical feathers to preserve Fai's body and sustain Sakura's life. Rescued by King Ashura of Celes Country, Yuui adopted the name "Fai," erasing his past. Ashura granted him the surname "Fluorite" (or "Flourite") and the title "D," signifying his status as Celes's highest magician. Ashura became a father figure, teaching Fai only lethal magic and advising that his smile could heal others. To counter Fei Wong's first curse, Ashura placed a phoenix tattoo on Fai's back to suppress his magical growth, intending himself to be the curse's target. Fai later used two feathers from Sakura's wings: one preserved Fai's body; the other created Chii, a being resembling his mother. Years later, Ashura transformed into a murderous entity, slaughtering Celes's populace. Unable to kill Ashura and fulfill the curse, Fai sealed him in eternal sleep. Fleeing to the Dimensional Witch Yūko Ichihara, Fai wished never to return to Celes, paying with his tattoo. He joined Syaoran and Kurogane's quest to collect Sakura's feathers, masking deep trauma with a carefree facade and teasing Kurogane with nicknames like "Kuro-rin," while concealing emotional detachment and profound self-loathing. In Tokyo, the clone Syaoran consumed Fai's left eye, containing half his magic, nearly killing him. To survive, Fai ingested vampire blood, becoming dependent on Kurogane's blood. His demeanor shifted to cold solemnity, and he addressed Kurogane formally to create distance. Returning to Celes, Kurogane killed Ashura, unknowingly activating Fei Wong's first curse and trapping the group. To escape, Kurogane severed his own arm to provide magic for dimensional travel. In Nihon Country, Fai sacrificed his remaining magic to Yūko in exchange for a prosthetic arm for Kurogane. After Celes, Fai reverted to playful nicknames for Kurogane and displayed genuine smiles. His magical abilities, tied to his blue eyes and capable of extending his lifespan, were permanently reduced by the eye loss and final sacrifice. He favored projectile weapons like darts and bows in combat, retaining strategic perceptiveness. Following Fei Wong's defeat, Fai continued traveling with Syaoran and Kurogane, liberated from his curses and past burdens.