Hikaru Mizuki is a character introduced during the second season of the anime. She is thirteen years old and has bluish-green hair and yellow eyes. Her background includes a formative experience in kindergarten when she played the role of Red Riding Hood in a play that ended in failure, which caused her to develop a deep-seated fear of performing in front of others. This stage fright, also known as public phobia, became a significant obstacle in her young life.

When first encountered, Hikaru presents herself as rude, bratty, and cocky, openly dismissing another idol as having poor skills and claiming to have no interest in an entertainment career. This arrogant exterior, however, is later revealed to be a defense mechanism masking her insecurity and deep-seated trauma from her past failure. Beneath this tough shell, Hikaru is passionate, sensitive, and easily frustrated, with a tendency to give up quickly when faced with pressure. Her personality exhibits a mix of traits, as she is also described as a kind, thankful, friendly, and helpful person once her trust is earned. She is cared for by a producer or manager, who recognizes her immense talent while lamenting her difficult personality.

Hikaru’s central role in the story is closely tied to her relationship with the main character, who helps her confront her fears. Initially acting as a rival, Hikaru is challenged to dance in front of a crowd, a situation that triggers her phobia and causes her to panic. Rather than remain a rival, the two characters form a bond. To help Hikaru overcome her stage fright, they become a duo, performing together as the idol group Kira Pika. This partnership proves successful, and the two become close friends. Hikaru is deeply affected by the group’s eventual disbandment, showing a fragile and sensitive side that emerged from her time spent with her supportive partner. A particular incident involving an accident with a boy named Wataru Tsubasa, for whom Hikaru has romantic feelings, leads her to quit being an idol. However, a final concert is held for Kira Pika before they split to pursue solo careers, and they remain good friends afterward.

Throughout the series, Hikaru demonstrates notable abilities as a performer. She is described as having great talent as an idol with significant potential, particularly in dancing and singing, and is able to perfectly imitate complex choreography. Her key development arc centers on overcoming her psychological trauma. With the encouragement of her partner, she is able to begin performing on stage, gradually conquering her public phobia through their collaborative work. Her personal growth is also reflected in her relationship with a pet cat. Initially disliking the animal, she eventually overcomes this and becomes friendly with it, which further highlights her underlying tsundere nature, where she behaves coldly but is actually warm-hearted.