Sanjo Yukari is a former employee of of Easter Company, the older sister of Sanjo Kairi, and Utau's manager. She came up with a new project, Black Diamond, to find the Embryo and mass-produce X Eggs. The CDs of the band were freely distributed and the people listening to it had their Eggs removed by force. As the band became more famous, their song is slated to be released to the Internet together with the unveiling of the band.

She and Utau resigned from Easter after Amu got Diamond back, and started their own music industry called Sanjo Productions. Yukari once dated Nikaidou Yuu, but the two have since broken up. She gets annoyed whenever their relation is mentioned.

Nikadou Yuu

Nikaidou Yuu is a former employee member of Easter. In order to find the Embryo, he joined Seiyo Elementary and became in charge of Amu's class in the disguise of a ditzy but kind-hearted teacher. His childhood dream was to become a robot engineer, but when his mentor quit, due to his ailing wife, and his parents opposed the idea, he lost sight of his dream and became a twisted person. He recovered with help from Amu and Su. He resigned from Easter Company and officially become the teacher in charge of Amu's class. A running joke is that he calls Amu Himamori, meaning "leisure time". He dated Sanjo Yukari before the series began, and they broke up.

Sanjo Kairi

Sanjo Kairi replaces Kukai as the new Jack's Chair when Kukai leaves for middle school. Kairi is tall, despite being two years junior to Amu. Unlike the spontaneous Kukai, Kairi is uptight, very organized, and blunt about faults. Even with these traits, he is so capable that Amu and Yaya call him "class president".

Kairi is the younger brother of Sanjo Yukari and was sent to spy on the Guardians. This wasn't his choice though, Yukari immediately begged him to transfer to Seiyo upon discovering that he had a Guardian Character. Since his sister is busy at work, Kairi takes care of the household work (and his sister) in her apartment. However, when he saw the true meaning of his "missions," he tries to rebel against Yukari, but not before he reveals his secret to the guardians when they accidentally discover him with Pestering CDs. He switches sides, after Amu convinces him he is a good person. Afterward, he leaves saying that he promised his parents and local classmates that he would return, but not before declaring his love for Amu saying that he shall return for her when he has become a man. He also declared a rivalry toward Tadase.

Mashiro Rima

Mashiro Rima replaces Nadeshiko as the new Queen's Chair. Although Rima is the same age as Amu, she is extremely petite and has relatively poor athletic ability. Most of the boys in her class admire her because of her beauty and passive personality, while the girls are annoyed by her because of her selfishness.

Because of a kidnapping incident that happened before she transferred to Seiyo Elementary, her parents pick her up after school, but since it interferes with their work schedules, they often argue about who cares more for Rima over work, resulting in Rima often having no one but Kusukusu as company for her secret interest in gag comedy. Later, she opens up to Amu and becomes friends with her.

When Yaya explains to Rima about Amu and Nadeshiko's friendship, she is shown to be jealous. At first, she is shown to have great dislike for Nagihiko because Amu told Rima and Yaya that he is Nadeshiko's twin brother due to a confusion between the two. That leads Rima to be protective over Amu. She tells Nagihiko that he is useless because his Guardian Character is still inside an egg, but gains respect for him later on.

Yuiki Yaya

Yuiki Yaya is the childish girl serving as the Ace Chair and is one year junior to Amu. Yaya often acts immature for her age, such as having an enormous sweet tooth, a great soft spot for items like ribbons as well as tending to be hyperactive. She is also a ballerina, though a rather clumsy one. She has a newborn baby brother named Tsubasa, who, she claims, gets all her parents' attention. It is because of this that her baby-like Guardian Character, Pepe, was born. Though she acts jealous around Tsubasa, Yaya does have a responsible side, once personally taking him to the doctor when he had a fever, as no other option was possible.

Souma Kukai

Soma Kukai is the upbeat, energetic, and friendly Jack's Chair of the Guardians. One year senior to Amu, Kukai helps Amu with her training as the Joker. Although he was the captain of the soccer club, Kukai loves and excels at all sports. At the end of the school year, Kukai graduates and goes on to middle school. However, Kukai returns to visit the Guardians from time to time.

Fujisaki Nadeshiko

Fujisaki Nadeshiko is a student in the same year as Amu and serves as Queen's Chair of the Guardians. When Amu rejected the offer to join the Guardians, Nadeshiko tries several tactics to convince Amu to join. The two become best friends and Nadeshiko looks over and supports Amu in her love life. However, before Amu and Nadeshiko enter the sixth grade, Nadeshiko leaves Seiyo Elementary for Europe to study dancing.

Nadeshiko is actually a boy named Fujisaki Nagihiko, called "Nagi" as a nickname by Amu and the girls. It is tradition in the Fujisaki family for males to be raised as females as part of their training so that they may play female roles in Japanese dance. Nagihiko's secret is known by his family, Kukai, Tadase, the school's principal Tsukasa Amakawa, and as of chapter 34, Rima. After Kairi leaves the Guardians, Nagihiko returns and is appointed as the interim Jack's Chair.

Hoshino Utau

Hoshino Utau is a junior high student model turned singing idol. She is actually Ikuto's younger sister, Tsukiyomi Utau. Utau had tried to find the Embryo to release her brother from Easter, but she never succeeded. Utau is very attracted to Ikuto and becomes extremely jealous of Amu because Ikuto shows an interest teasing her. However, she eventually accepts Amu.

She was the vocalist of the indie band "Black Diamond" which is produced by her manager, Sanjo Yukari, as a method of using the CDs of their music to draw the eggs out of children and make them into X Eggs. When the plan fell apart, Utau quit Easter with her manager and became a singer on her own, without Easter contracting her.

Tsukiyomi Ikuto is a teenage boy contracted by Easter to find the Embryo. He often helps Amu even though he works for Easter. Ikuto actually despises Easter and tries to wrench himself free from them by trying to find the Embryo to grant his own wish. He possesses the Dumpty Key which pairs with Amu's Humpty Lock, but currently, it doesn't fit in the keyhole. Like his father, Ikuto is a skilled violinist. The Dumpty Key used to belong to Tadase's father, but Ikuto took it from Tadase. His mother, upon marrying someone else after they found her husband's violin in a foreign country and believing that he would not come back, bound her children into working for Easter. In the series it is seen that Ikuto is always trying to stay away from his mother. Ikuto's personality is aloof, stoic, and a little naughty. He likes teasing people, especially Amu and Tadase. He is also the older brother of Hoshina Utau. He is shown to have feelings for Amu -- he confessed that he liked her in the same chapter Tadase did, but unlike Tadase's confession, Amu didn't believe Ikuto's. That led Ikuto to compare his situation with "the boy who cried wolf". When he made fun of Tadase's confession and told him that he stayed at Amu's house for three days, Amu yelled at him in anger, saying that she never wanted to see him again. He later surrendered himself to Easter, not wanting to get anyone else involved in the mess he made. In the manga timeline, it is shown he Character Transformed with a new black Guardian Egg to become Death Rebel, shocking Amu.

Hatori Tadase

Hotori Tadase is a boy in the same year as Amu and serves as King's Chair of the Guardians. Like Amu, he is actually a shy person and is not good at public speaking; instead, he Character Changes with his Guardian Character, Kiseki. Although he is popular with the girls, when a girl confesses their love to Tadase, he will have Kiseki reject her. However, whenever he hears the word "prince", he Character Changes into an egotistical king who seeks world domination. Amu develops a crush on Tadase soon after she transfers into the school. His love interest is Amulet Heart, Amu's Character Transformation with Ran, but it later becomes Amu herself. Tadase has known Ikuto and Utau since childhood, but he does not talk about it in detail until the Guardians are about to face Utau in their final battle. In chapter 28 of the manga, when he visits Amu's house he confesses that he likes her and not just Amulet Heart. When Ikuto makes fun of confession and tells him that he stayed over at Amu's house for three days, Tadase gives Amu a saddened look and runs away. Amu and Tadase reconcile soon after, though. Later on, he agrees to help Amu save Ikuto from Easter. When Tadase was facing against Ikuto, his staff becomes a sword called, Royal Sword.

Hinamori Amu

Hinamori Amu, the series' protagonist, is a student of Seiyo Elementary. Amu's classmates see her as "cool and spicy", but Amu is actually extremely shy and timid. Part of the reason for this misunderstanding is the trendy punk goth clothing her mother buys for her as well as the way in which she expresses her shyness and avoids doing new things which people interpret as 'cool'. However, when Amu wishes for the courage to be reborn as her would-be self, three colorful eggs appear the next morning, which hatch into Amu's three Guardian Characters: Ran, Miki, and Su. When one of her Guardian Characters Character Changes with her, she gets embarrassed because they make her speak in ways that she thinks are "totally out of character".

Because of her three Guardian Characters, Amu became a member of the Guardians, the school's student council, although she refused to join at first. Amu's position with the Guardians is the Joker. Her task, as the Joker, is to search for and purify X Eggs, X Characters, and in the second season, Mystery Eggs, the corrupted forms of people's would-be selves. Ran, Miki, and Su help Amu with her task through a process called a Character Transformation, which is enabled by the Humpty Lock and grants Amu special abilities depending on the Guardian Character. Later on, Amu also creates a fourth egg, known as Diamond. In the second season, when Amu shows her true potential, the Humpty Lock increases it's power. Thus, new transformation scenes are used.

Amu's two main love interests are Tadase Hotori and Ikuto Tsukiyomi. However, she has minor crushes, such as Kairi Sanjo, Kukai Souma, and Nagihiko Fujisaki but shows more friendliness. Amu's primary rival is Utau Hoshina, an idol singer for Easter who is jealous that Ikuto shows an interest in Amu instead of her. Amu gains the Dumpty Key (from Yoru) and tries to use it and unlock the Humpty Lock.

PLOT

The heroine of the story, Hinamori Amu, is a student at Seiyo Elementary. At first glance, her classmates deem her "cool and spicy" and rumors speculate about her personal life. However, her real personality is a very shy girl who has trouble showing her true personality. One night, Amu wishes for the courage to show her "would-be" self, and the next morning finds three brightly colored eggs—red, blue, and green—in her bed. At first, she is alarmed, but realizes she must have really wished to change. These eggs hatch into three Guardian Characters: Ran, Miki, and Su. The Guardian Characters aid Amu in discovering who she truly is and help fulfill Amu's dreams. Amu's life becomes much more complex as she struggles to deal with her "would-be" selves and the Seiyo Elementary's Guardians, who recruit Amu to search for X Eggs and X Characters, the corrupted forms of peoples' dreams.

Meanwhile, the Easter Company is extracting people's eggs in search of a special egg called the Embryo. The Embryo is believed to able to grant any wish to the one who possesses it. However, the process creates X Eggs and X Characters.