Fai D. Fluorite, also known as Fai D. Flowright, hails from Valeria Country, born Yuui, the younger twin of Fai. Their birth was considered a curse in Valeria, triggering their mother's suicide and widespread misfortune. The Valerian king imprisoned the twins separately within a magic-negating tower, seeking to perpetuate their suffering. Fei Wang Reed later offered freedom to one twin. Yuui sacrificed himself for his brother's escape, but Fei Wang manipulated Yuui's memory, making him believe he had chosen to save himself. Consumed by guilt, Yuui adopted his brother's name. Fei Wang Reed placed two curses upon him: one demanding he kill obstacles on his journey to revive Fai, and another erased from his memory.

King Ashura of Celes Country rescued Yuui, naming him Fai D. Fluorite after the gemstone fluorite. Ashura trained him in magic, though Fai mastered only lethal spells. To suppress Fai's burgeoning power and ensure the first curse would activate against himself, Ashura placed a Phoenix tattoo seal on his back, erasing this knowledge. When Ashura transformed into a destructive entity due to his magic, Fai refused to kill him, instead sealing him away and fleeing Celes to avoid confronting Ashura's inevitable awakening.

Traveling to collect Princess Sakura's feathers, Fai maintained a cheerful, enigmatic facade while emotionally distancing himself from companions Syaoran, Sakura, and Kurogane. He avoided using magic under a self-imposed vow, breaking it solely to protect others, such as shielding the group in Lecourt Country. This carefree demeanor masked profound self-loathing and disregard for his own life, though Kurogane sensed his hidden turmoil and urged him to face his present.

In the desolate, acid rain-scarred world of Tokyo, Fai's past and curses converged critically. The clone Syaoran, acting under Fei Wang Reed's control and having lost his artificial heart, attacked Fai to reclaim power, consuming his left eye—which contained half of Fai's magic—to enhance his own abilities. The injury left Fai near death. To save him, Kurogane offered his blood through Mokona's intervention, transforming Fai into a vampire reliant on Kurogane's blood for survival. This transformation deepened Fai's emotional isolation; he ceased using nicknames for Kurogane, deliberately straining their bond to prevent deeper attachment.

The trauma in Tokyo intensified Fai's guilt and self-imposed solitude, yet Kurogane's unwavering support began to challenge his emotional barriers. Following these events, Fai gradually reclaimed aspects of his earlier persona, resuming his affectionate teasing of Kurogane while integrating his traumatic experiences into a more resolved identity. His journey embodies the struggle between inherited curses, manufactured guilt, and the redemptive influence of companionship.