Kagari Shiina, a war orphan from the Beta Attractor Field’s World War III, loses her biological parents and original identity when her family registry is destroyed. Adopted in 2032 by Mayuri Shiina—a caregiver at her orphanage—she inherits the name "Kagari" ("bonfire"), symbolizing Mayuri’s wish for her to illuminate darkness. Her childhood is marred by covert military experiments under Dr. Alexis Leskinen, who implants Amadeus AI applications into her psyche while falsely treating her PTSD. Pale-skinned with long red hair and blue eyes, her striking resemblance to Kurisu Makise sparks speculation, though no genetic link exists. In one timeline, she surgically adopts Yuki Amane’s appearance for subterfuge. Emotionally volatile from Leskinen’s brainwashing, she hears his commands as divine edicts, yet her fierce loyalty to Mayuri—whom she calls "Mommy"—sometimes disrupts this conditioning. PTSD manifests as claustrophobia, emotional collapses, and identity fractures when Kurisu’s memories invade her consciousness. Time-traveling to 1998 with Suzuha Amane to avert the Y2K crisis, Kagari panics over potential worldline shifts erasing Mayuri. This triggers her programming, driving her to assault Suzuha and reconnect with Leskinen, who subjects her to further experiments under the identifier "K6205." Captive, she scrawls desperate blood messages to Mayuri before escaping. Her accidental encounter with a young Okabe Rintaro seeds his "Hououin Kyouma" persona and a causal loop: a melody she teaches him echoes through time, later reaching Mayuri via Yuki Amane and Okabe’s mother. Worldline divergences reshape her fate. In *Recursive Mother Goose*, a near-death experience restores her erased memories, sparking a tearful reunion with Mayuri. *Promised Rinascimento* pits her against forces seeking to overwrite her identity with Kurisu’s digitized consciousness. Posing as Yuki in *Vega and Altair*, she navigates unrequited feelings for Itaru Hashida. Stratfo’s influence occasionally hardens her into a tactical operative, though she shields Mayuri relentlessly. Her fragmented existence intertwines with pivotal events—Operation Arclight, the suppression of Kurisu’s memories—where she counters threats like Dr. Reyes. Across all realities, her anchor remains unwavering: protecting the bond with Mayuri, even at mortal risk.