Nagisa Motomiya is a main protagonist of the AKB0048 series. She is a thirteen-year-old girl from the planet Lancastar who becomes a 77th generation understudy, or trainee, for the idol group AKB0048. Her background begins four years before the main story when she, along with her friends Orine Aida and Yuuka Ichijo, is invited by Chieri Sono to watch an illegal AKB0048 performance at a mining site. That concert inspires her to pursue a life as an idol despite entertainment being banned by the totalitarian Deep Galactic Trade Organization. Nagisa’s father initially disapproves of her dream, but she persists and eventually passes the group’s auditions alongside her friends.

Nagisa’s personality is friendly, innocent, and somewhat clumsy. She is often absentminded and does not always take training as seriously as her peers, which leads Yuuka to frequently scold her. Despite this, her love for AKB0048 is steady and sincere, and she is determined to give her best. Her personal motto is that even if she trips and falls, she will show everyone her spirit. Nagisa is also naive about competition; she dislikes general elections and rivalries because she fears they might turn her into a vengeful person. Her motivation is rooted in the freedom that music and performance represent, and she wants to bring joy to others through her singing.

In the story, Nagisa goes through significant challenges and growth. During the Lancaster concert arc, her father is captured by the authorities, which causes her to become deeply worried and temporarily lose her voice. With encouragement from her friends and the inspiration of Acchan’s legacy, she regains her confidence and her voice, performing with renewed strength. By the end of the second season, Nagisa’s growth as a performer is recognized, and she succeeds the role of Atsuko Maeda, becoming Atsuko Maeda the 14th. This succession marks her as the new center of the group, taking on the responsibility of carrying forward the spirit of the original member.

Nagisa’s key relationships include her close bond with Chieri, Orine, and Yuuka, who form her core support group. She also interacts with the 75th generation trainees and the successors, learning from them and earning their respect. Her father, though initially opposed, eventually comes to understand her passion. In terms of abilities, Nagisa is not naturally a strong singer at first, but she steadily improves during her training. Her singing voice becomes her most notable asset, connecting her to the Kirara, a mystical entity that senses emotions and enhances performances. This power allows her to inspire hope and resistance in audiences across the galaxy.