Kozue Shirakaba, the sole daughter of Takara Elementary School teacher Hiroki Shirakaba, carries a name reflecting nature—her surname merging "white" (白) and "birch" (樺), while her given name means "treetop" (梢). Her life pivoted during the May 10, 2020 fire at Takara Elementary, where she became trapped inside. Asumi Suido, a fellow student, raced into the flames to save her. When collapsing debris threatened Kozue, Asumi shielded her with her own body, sacrificing her life. Shuta Aoi arrived moments later, pulling Kozue from the wreckage but unable to rescue Asumi. Though physically unharmed, Kozue bore deep psychological scars.

Consumed by survivor's guilt over Asumi's death, Kozue withdrew entirely from school and social life, retreating into isolation at home. She revered Shuta as a hero for his rescue attempt despite his failure to save Asumi. Another devastating blow followed when her father Hiroki perished in a separate crisis, sacrificing himself to ensure Kozue's survival during a tornado.

Gradually, Kozue began rebuilding her fractured world. She channeled her resolve toward art, eventually enrolling in art school—a step symbolizing her emergence from trauma and commitment to a future defined not by loss, but renewal.