Kaori Kananase serves as the older sister to protagonist Yu Kananase. Their father, scientist Masaki Kananase, developed "Remake," a technology enabling soul transfer between bodies and memory manipulation. After a traumatic event involving their parents, Kaori and Yu became significantly estranged, creating lasting emotional distance.

She commands the 18th squad within the high-ranking leadership of the International Military Organization (I.M.O.). Kaori orchestrated Yu's recruitment into the I.M.O., deploying his childhood friend Satoru Tachibana to facilitate his enlistment. Her core motivation centers on accessing Yu's unique "Life Data," information implanted within him through the Remake process.

Her authority places Kaori at the heart of escalating global conflicts over control of Remake, involving rival superpowers and competing scientists. During the series' latter half, she becomes physically integrated into the I.M.O.'s advanced computer system, "Ragnarok," remaining connected throughout this story phase. This role emphasizes the series' incorporation of Norse mythological elements, as Ragnarok references its apocalyptic namesake. Kaori's actions and decisions are consistently driven by the complex legacy of her father's work and its profound implications for both Yu and the world.