Uta Koizumi, an 11-year-old from Miyagi Prefecture standing 147 cm tall, started her career as a child actress at age four. Her numerous TV drama roles brought significant popularity, but her mother's management and high expectations strained their relationship. Feeling confined by her "child actress" image, Uta seeks reinvention by pursuing idolhood.

She enters a nationwide idol audition as Tohoku's representative, hiding her singing and guitar skills to preserve her established persona. During the first round, she forms the subunit GAPsCAPs with Mako Toma and Shiori Yamaga, playing guitar. Their collaboration sparks conflicts due to clashing personalities, ages, and backgrounds—particularly with the equally proud Shiori.

A turning point occurs when Uta secretly steps in to perform guitar and vocals for a drama theme song after the scheduled musician falls ill. This reveals her hidden talents, surprising viewers and industry figures. Her mother acknowledges the positive audience response, increasing support for Uta’s idol aspirations and strengthening her resolve to redefine herself beyond acting.

Uta exhibits a strong-willed, prideful demeanor from years in entertainment, balanced by childlike curiosity and vulnerability. Her hobbies include reading Wikipedia, collecting trivia, and studying voice acting through anime to inform performances. She identifies with the butterfly as a symbol of reinvention and lives by her motto: "There is no greater talent than hard work."

As the youngest contestant in her group, peers call her "sensei" due to her extensive experience, contrasting her age and tenure. Throughout the competition, Uta gradually embraces authenticity, moving beyond her managed image to showcase her multifaceted talents.