Uori Mukae is a 14-year-old middle school student born on December 2 in Kamakura City, Kanagawa Prefecture. Standing 158cm tall, she serves as the center for the idol unit Ongaku Shoujo, with navy blue as her theme color. Uori possesses exceptional singing and dancing skills befitting her role and is also a proficient cook who maintains a personal recipe book. Her personality blends intense dedication to her work with a confrontational streak, particularly directed at Hanako Yamadagi, whom she perceives as not taking idol activities seriously; this fuels her catchphrase, "Don't take idols lightly!" Despite this friction, Uori gradually connects with Hanako through anonymous interactions on the Idol Bulletin platform under the username "Chorigana." She exhibits shyness when Hanako compliments her recipe book or hugs her in an onsen.

Uori deeply admires and emotionally depends on her older sister, Kiri Mukae. She experiences strong jealousy when Kiri bonds with others, such as spending a night with Hanako, leading Uori to feel gloomy during their separation and struggle to sleep while longing to be Kiri's "number one." This possessiveness surfaces subtly, like showing displeasure when Hanako complimented both sisters. Uori navigates these complex emotions while maintaining her position as center and reconciling her high standards for idol dedication with emerging camaraderie. She released a solo character song titled "poppin' rain," a pop tune conveying an idol's resilience to smile brightly even during challenging times.