Chloe von Einzbern, alias Kuro, emerges as a splintered persona born from Illyasviel von Einzbern’s suppressed memories and identity. Her existence traces to a protective seal placed by Illya’s parents, Kiritsugu Emiya and Irisviel von Einzbern, to obscure their daughter’s role as a Holy Grail vessel and grant her an ordinary childhood. Over time, these sealed fragments coalesced into a separate consciousness, which materialized physically when Illya inadvertently activated an Archer Class Card during a magical upheaval. The split birthed Chloe, who inherited Illya’s original name and memories but manifested a tanned complexion, golden eyes, and a sharper, more assertive demeanor.

Driven by survival instincts, Chloe initially plotted to erase Illya, perceiving her counterpart’s yearning for normalcy as a threat. Empowered by the Archer Card’s abilities—projecting weapons, teleportation, and combat expertise drawn from EMIYA—she relied on frequent mana absorption, often through kissing, to sustain her unstable form. A shared curse that tethered her agony to Illya’s well-being compelled an uneasy alliance, prompting Chloe to masquerade as Illya’s cousin while covertly unsettling her life.

Irisviel later unveiled Chloe’s true origin: she was the miscalculated remnant of Illya’s intended destiny as the Holy Grail. Facing disintegration from mana scarcity, Chloe’s survival depended on Illya voluntarily sharing her energy, a pact that culminated in Chloe wishing for familial belonging. This desire anchored her existence, integrating her into the Einzbern household as Illya’s adoptive sister.

Chloe’s personality blends calculated calm with playful manipulation, contrasting Illya’s naivety. Though outwardly provocative and self-assured, she harbors insecurities rooted in her fragmented origin, yearning for purpose and acceptance. Her rivalry with Illya masks latent protectiveness, evident in alliances to safeguard Miyu and combat external threats. Bonds with figures like Miyu and Shirou reveal a capacity for loyalty and understated affection, though her blunt demeanor frequently sparks humor or friction.

Across subsequent narratives, Chloe navigates her evolving role as both family member and ally. Parallel-world collaborations with Bazett and Gilgamesh showcase her tactical ingenuity and battlefield prowess. Her enduring mana reliance on Illya underscores their entwined destinies, while spin-offs and crossovers reaffirm her unique identity—a shadow given form, yet distinct in her resolve to carve a place within the world she was born to inherit.