Yuiri Haba serves as a Sword Shaman of the Lion King Agency, hailing from High God Forest. Unlike most peers there, she possesses a living family—parents employed as Lion King Agency office workers and a younger brother near her age—which spared her from high-risk missions due to institutional consideration. Her foundational training occurred at High God Forest, distinct as she was not an orphan like program contemporaries. She forges close bonds with key figures: Shio Hikawa, her frequent mission partner and High God Forest classmate; Yukina Himeragi, her junior affectionately nicknamed "Yukii"; Sayaka Kirasaka, another training-era classmate; and Glenda, who later exhibits particular fondness for her. Yuiri harbors romantic feelings for Kojou Akatsuki, the Fourth Primogenitor, initially encountering his reputation through High God Forest rumors. Nominated but rejected as his observer due to her inability to wield a Schneewalzer effectively and the Lion King Agency’s reluctance to endanger her given familial ties, she indulges in romance manga-fueled fantasies about Kojou and displays jealousy toward his closeness with Yukina. Her missions span critical arcs: capturing Gajou and Nagisa Akatsuki at Kamioda Temple during "The Fugitive Fourth Primogenitor"; surveilling Gajou with Shio in "Knight of Sinful God" before Hisano Akatsuki redirected her to protect Nagisa. At an Avalon sealing ceremony, she perceptively suggested its protective nature over menace, later rescuing a mysterious girl from demon beasts and safeguarding wounded SDF personnel under Hisano’s orders. During "The Roses of Tartarus," she and Shio escorted Glenda via passenger ship, encountering Sayaka before the vessel collided with wreckage. In "A War of Primogenitors," they investigated Glenda at Blue Elysium, confronting Veres Aladar of the Holy Ground Treaty Organization. Overwhelmed in combat, Yuiri directed Glenda to seek Kojou and Yukina’s aid before unconsciousness. She wields Rosen Chevalier Plus, a mass-produced anti-demon weapon derivative of Lustrous Scale. Her name Yuiri signifies "sole, only" (唯) and "village" (里), while Haba means "feather" (羽) and "wave" (波). Privately, she reads romance manga—a hobby shared solely with Shio. Her long-term trajectory culminates in marriage to Kojou Akatsuki, joining his future partners like Yukina Himeragi and Asagi Aiba.