The series is about a young girl named Sora Naegino who comes from Japan to the United States in search of her dream. She wants, with all her heart, to be a member of the acrobatic circus that performs at the famous Kaleido Stage (similar to the Cirque du Soleil) located in the fictional city of Cape Mery, California With the help of her friends, Sora struggles to make this dream come true.

Sora Naegino (苗木野そら, Naegino Sora^?)

Sora is the main character of Kaleido Star. Her parents took her to Kaleido Stage when she was young. Although they died shortly thereafter, and Sora went to live with her aunt and uncle, Sora is inspired by this childhood memory to become a member of the Stage when she reaches adulthood. With her aunt and uncle’s hesitant approval she travels to the United States to audition. While she wanders around lost, her bag is stolen. As a consequence of chasing the thief and speaking to the police, she is late to the audition; Layla will not allow her to audition, but the owner Kalos gives her a chance to perform in the actual show. Most of the cast do not accept Sora at first because of the special circumstances through which she joins; Sora wins them over with persistence and hard work along with a magnetic personality. In the beginning of the series Sora is the only one who can see the magical stage spirit Fool. This character reveals she has been chosen by the stage. In the first season, Fool reveals only she can perform the Legendary Great Manuvor with Layla. In the second, he reveals that she has the potential to become a “true star”.

Layla Hamilton (レイラ・ハミルトン, Reira Hamiruton^?)

Layla is an accomplished and seasoned performer. She is a stubborn character and plays an antagonist-like role in the beginning of the story, but like many of the other characters, she befriends Sora. Layla is the daughter of Mr. Hamilton, a wealthy hotel chain owner; he would prefer Layla to be an actress and is frequently trying to push her into doing so. Layla eventually stands up to her father and rejoins the circus; she loves the Kaleido Stage because she clearly remembers how her deceased mother enjoyed going there. At the end of the first season, after attempting the great Mystical Act and seriously injuring her shoulder Layla gives up the circus and retires to Broadway.

Mia Guillem (ミア・ギエム, Mia Giemu^?)

Mia is a close friend of Sora’s. In the second episode, Mia accepts Sora’s presence on the stage after Sora attempts to perform the Golden Phoenix. Later in the series, Mia becomes passionate about writing the scripts for Kaleido Star’s performances. She occasionally has inner conflicts between performing and attending to her sick grandmother.

Anna Heart (アンナ・ハート, Anna Hāto^?)

Anna is also good friend of Sora’s. She too, like Mia, comes to accept Sora after the second episode. Anna is talented in many areas and frequently plays more serious parts. Anna truly wishes to perform comedy and usually tries to get Mia to write comedy into her parts. The request is almost always denied. Anna takes her love of comedy from her estranged father Jack, a stand-up comedian.

Yuri Killian (ユーリ・キリアン, Yūri Kirian^?)

Yuri, like Layla, is an experienced performer. During a flashback, it is revealed that his father died attempting the Mystical Act, and he never forgave Kalos for letting his father try. He plays a pivotal role in the second half of the first season when he betrays the stage, first by stealing away a good portion of the cast and later by buying out the stage and taking control of it. He later agrees to return it to Kalos if Layla and Sora accomplish the same Mystical Act that caused his father’s death, and when they manage to do so he fulfills his promise. In the second season, Yuri helps Sora get into the Circus Festival in Paris. He appears to be a bitter rival of Leon’s, and feels that he is responsible for Leon’s sister’s death.

Fool (フール, Fūru^?)

Fool is the mysterious spirit of the stage. He is about the size of an action figure, and appears as a type of jester or clown. He appears to Sora shortly before she appears on the Kaleido Stage for the first time. Fool is invisible to everyone but those who are destined to do great things on the stage and/or whose heart is completely dedicated to the stage. Although a ghost, Fool is a pervert who tries many times throughout the series to see Sora, and sometimes her friends, naked (usually by suggesting that they should take a shower). Sora is quick to prevent Fool from peeking in any given situation by trapping him somewhere or rebuking him forcefully, most often in a comedic, slapstick fashion. Later in the first season, Layla becomes capable of seeing Fool as well; the same happens to Rosetta at the end of the second season. In his more useful moments, he acts as a fortune teller, revealing possible futures to Sora (in the first season he reads the future from Tarot cards, in the second season he reads and reveals the hidden workings of intercharacter relationships via Astrology). He is also the one who explains the inner mechanics of the Mystical Act to Layla and Sora in episode 25, An Amazing Bond.

Sarah Dupont (サラ・デゥポン, Sara Dyupon^?)

Sarah is the diva of Kaleido Stage as well as the building manager for the dorms where everyone lives. Many want Sarah to sign on record label because she is so gifted in the singing department but she stays true to Kaleido stage. She is an avid fan of the martial arts, and frequently proposes bizarre alternative methods to help Sora achieve her objectives. She’s well acquainted with Kalos and has been with the Stage from the beginning, when she and Kalos were performing on the street with another friend. This friend returns once to try to persuade Sarah to leave Kaleido Stage with offering her a singing career, but she refuses.

Ken Robbins (ケン・ロビンス, Ken Robinsu^?)

Ken is the stage manager for Kaleido. He is unable to perform due to a heart condition. Ken also greatly admires Sora, in many respects, but never has the guts to confess his true feelings for her. This does not stop him from doing everything he can to help her out. Frequently he acts as her personal trainer, warning her of the dangers she might encounter. Many times he acts as the voice of reason for the group.

Kalos Eido (カロス・永戸, Karosu Eido^?)

Kalos is the head manager of the entire Kaleido Stage and gives Sora many helpful pieces of advice throughout the anime. He also maintains high expectations of everyone he encounters. Before Kaleido Stage, Kalos used to perform on the street with Sarah. Their past relationship is rather vague. Kalos is also the one who trained Yuri’s father for the Mystical Act. He is the only person who can tell Layla and Sora how to train for the act.

Policeman (Jerry) (ポリス, Porisu^?, Police)

The character Jerry is self-described throughout the show as Sora’s “#1 fan”. He has helped and supported her from episode one. He is also secretly in love with Kate, a doctor who occasionally appears to help cast members through physical injuries. In the second season, the policeman gathers the courage to ask her to marry him.

Marion Benigni (マリオン・ベニーニ, Marion Benīni^?)

Marion is a young girl living near the stage. Her father works on sets, but her mother (a former trampoline artist) is dead due to an accident. Like many of the others, Marion doesn’t accept Sora at first, but is quickly won over to her side. In the second season Marion begins to perform with the group on the Children’s Stage.

Jonathan (ジョナサン, Jonasan^?)

Jonathan is a baby seal that Sora picked up one day. Unable to keep pets, Sora tries to hide him. However, the secret is revealed and instead of kicking him out, Marion’s father builds a tank for him. He is capable of doing many tricks and sometimes seems more coordinated than Sora, creating comical performances that the children attending love. During the second season, Jonathan becomes closer to Marion and refuses to perform with anyone else.

Rosetta Passel (ロゼッタ・パッセル, Rozetta Passeru^?)

Rosetta is a world champion diabolo performer. After her first Kaleido performance Kalos kicks her off the stage because she was unsatisfying: he explains despite being perfect in the technical fields, her act lacked passion and everyone was bored by her act. Sora takes the girl under her wing, teaching her how to put audience enjoyment before technical perfection. In return, Rosetta teaches Sora diabolo, which Sora returns to when she needs help learning new acts. Rosetta returns in the second season wishing to become a trapeze artist and follow in Sora’s steps.

May Wong (メイ・ウォン, Mei Won^?)

First appearing in the second season, May is a new recruit who challenges Sora’s position. Sora and May have a tense rivalry for most of the second season, which aids both in becoming better performers. May turns out to be exceptionally talented and becomes Leon’s partner for the Dracula show. During one of the performances, Leon drops her dislocating her shoulder. This allows Sora to obtain the spot for the Circus festival. May, understanding that Leon abandoned her due to her selfish and childish attitude, refuses to give up her spot and overtakes Sora with a new one armed trick finally besting Sora and putting her on top. As she does so, she lays off her arrogance and becomes a better person.

Leon Oswald (レオン・オズワルド, Reon Ozuwarudo^?)

Leon is a trapeze performer who arrives in the second season. He comes off as arrogant, refusing to perform with Sora because she is not skilled enough for him. His true desire, however, lies in a promise he made to his dying sister Sophie: to see the Angel’s Act, an unrivaled and beautiful trapeze act they had developed, completed. He’s a rival of Yuri Killian, whom he blames for the death of Sophie in an accident.

Mr. Kenneth (ケネス, Kenesu^?)

Mr. Kenneth is an elderly man he is the representative for the Stage’s stockholders and also said to be the producer or the stage. Putting him in a position as high as Kalos or even higher. He has great experience in the show business and also often aids Sora like Kalos. He also personally knows Ken but never calls him by his real name.