When Sora Naegino was little, her parents took her to Kaleido Stage to watch the stage version of Alice in Wonderland. Although they died shortly thereafter and Sora went to live with her paternal aunt and uncle (who couldn't have children of their own, so they took her in to give her a family), she was inspired by this single childhood memory and thus gained the dream of someday becoming a member of Kaleido Stage.
The story starts when sixteen year old Sora, with her aunt and uncle's hesitant approval, travels to the United States to audition. As a consequence of chasing a thief and making friends with a local police officer, she comes late to the audition. Though stage manager Ken Robbins is willing to give her a chance, Kaleido Stage's top star, Layla Hamilton, does not allow her to audition. However, after Sora accidentally causes another performer to become injured just before a show, the owner, Kalos Eldo, gives her the chance to replace her and perform in the actual show.
Most of the cast do not accept Sora at first, because of the special circumstances through which she joins. Yet in time, Sora manages to win them over with her persistence, hard work, and magnetic personality.
Sora is the only one who can see the magical stage spirit Fool, because, as he states, she has been 'chosen' by the stage. In the first season, Fool reveals that only she can perform the Legendary Great Maneuver with Layla. After much hardship, they successfully perform the technique for all to see, thus reestablishing Kaleido Stage's merit and saving it from shutting down for good. However, a steep price is paid; the shoulder injury that Layla sustains during practice becomes so bad that she is forced to end her career as a performer. While this news devastates Sora, Layla gives her strength and courage once again by asking her to become her dream - become a "true star". The second season, thus, marks Sora's new battle to achieve her new goal.
Throughout the series, Sora becomes better and better. But in episode 29 of Season 2, Sora meets a girl named May Wong who automatically declares herself as Sora's rival. May blames Sora for Layla's injury and is bitter that Sora was the one who was able to become the partner of her idol; according to May, Sora's lack of talent is the reason why Layla was injured, and so she makes it her goal to become the top star and kick Sora out.
The two duel many times throughout the series, both of them striving to become the partner of the talented but cynical Leon Oswald, which they believe will determine which girl has the better skill. However, while trying to follow in the path of conflict that Layla set out for her, Sora quickly becomes disillusioned, and so disheartened that she almost leaves the Kaleido Stage. At home, she realizes that her goal is to become the true star - *not* by fighting other performers, but by creating a stage free of conflict that exists only to bring joy to both the audiences and the performers, and she learns that an act that can bring about such a stage is called the Angelic Act.
After much hard work and after defeating her former idol Layla in one last duel, she finally performs the Angelic Act and in doing so touches the hearts of the audience, performers and even former enemies - like May herself.
By the end of the series, Sora becomes the Top Star, thus beginning a new 'era' for Kaleido Stage.