Yor Briar, later Yor Forger, was orphaned with her younger brother Yuri during the Ostanian-Westalis war. Forced into a parental role early, she raised Yuri alone in Nielsberg. To support him financially and shield his innocence, she accepted training from the enigmatic Shopkeeper, joining the Garden assassin organization as "Thorn Princess." Her earnings funded Yuri's education and well-being, culminating in their relocation to Berlint for his college attendance.

Professionally, Yor maintains strict duality. Publicly, she works as an unassuming, aloof clerk at Berlint City Hall, minimizing interactions to preserve her cover. Privately, she executes high-risk assassinations for Garden with lethal efficiency, politeness toward targets, and superhuman capabilities: immense strength (crushing pumpkins or skull-impaling strikes with stiletto daggers), remarkable speed and agility for parkour or vehicle pursuits, heightened reflexes, advanced pain tolerance, extensive durability, and resistance to most poisons through acquired immunity. She struggles to control her strength in daily life, causing accidental damage or injuries.

Socially awkward and lacking common sense, Yor often misinterprets cues and shows gullibility, readily believing fabricated cover stories. Her problem-solving instincts initially default to violent assassination fantasies for mundane issues, though she consciously suppresses these impulses. Post-Yuri's independence, loneliness drove her to seek companionship. Pressured by coworkers about her unmarried status and fearing state suspicion, she impulsively recruited widower Loid Forger—met at a tailor shop—as a fake boyfriend. Their arrangement rapidly escalated to a legal, loveless marriage after Loid introduced himself as her husband publicly, serving mutual interests: disguising her assassinations while aiding Loid’s fabricated nuclear family for his daughter Anya’s Eden Academy enrollment.

Joining the Forger household spurred personal growth. Despite domestic insecurities—notably inedible cooking—Yor developed genuine maternal affection for Anya. She actively improved parenting and homemaking skills through cooking lessons and marital advice from coworkers. Her protective instincts flared against threats to Anya, prompting physical interventions against bullies or kidnappers and self-defense training upon Anya’s request, strengthening their bond. Concurrently, her relationship with Loid deepened beyond convenience into mutual trust, reliance, and romantic tension—both concealing secrets (his espionage, her unawareness of it). Yor felt jealousy toward Loid’s colleague Fiona Frost, desired his emotional dependence, reassured him during parental doubts, and voiced happiness in their partnership.

Her bond with Yuri remained deeply affectionate yet complex. Unaware of his obsessive sister complex and Secret Police role, she cherished their connection but enforced boundaries against his intrusiveness toward the Forgers. She continued hiding her assassination work to protect his peace, mirroring his secrecy about his profession.

A core internal conflict emerged as her attachment to the Forgers grew. Garden policy mandated her removal if she sustained injuries unexplainable in civilian life, creating a psychological barrier during missions where she subconsciously held back. Facing near-death against fellow assassins during the cruise ship arc, she realized her motivations now included safeguarding her newfound family alongside Yuri’s innocence. She resolved to persist in her work, trusting Loid would understand her commitment to fighting for others’ safety despite personal cost.

Yor embodies contradictions: extreme professional violence versus personal kindness; social ineptitude alongside tactical intuition; profound familial love coexisting with duty-bound self-sacrifice. She gradually integrated these facets, evolving from viewing her family as camouflage to embracing them as her emotional core while continuing her assassin role with renewed purpose.