Shugo Chara!

People view Amu Hinamori as a "cool and spicy" girl; she is actually timid and easily scared. When she wishes to have the courage to show her "true" self, she discovers three colorful eggs -red, blue, and green- in her bed. At school, the eggs draw the attention of Tadase Hotori, the most popular boy in school, who Amu has a crush on.

Nadeshiko Fujisaki, queen of the school, invites Amu to tea at the Royal Garden, where she'd meet the Student Council Guardians. However, during P.E. class, the blue egg begins to hatch, and its' Guardian Character runs away!

Nadeshiko tells Amu that the two should become friends, but Amu sees it as a trick to get her to join the Guardians. Ikuto Tsukiyomi, the mysterious stranger from last time, interrupts the two and attempts to steal the last of Amu's eggs.

Amu joins the Guardians as "The Joker", much to her dismay, and they inform her about the mysterious X Eggs. Ikuto tries to make amends with Amu. A mysterious new teacher named Yuu Nikaidou joins Amu's class.

Amu and Nadeshiko attend Kukai's soccer team practice. One of Kukai's friends, Yamada, is deeply upset when the coach announces he didn't make it to the team. Nikaidou takes advantage of Yamada's feelings and extracts Yamada's Heart's Egg, turning it into an X Egg.

Amu accompanies Yaya to the guardian's ballet class. During practice, the class's prima Maika Himekawa sprains her ankle and Yaya is chosen to be Maika's stand-in for the upcoming performance. Meanwhile, Nikaidou meets with Ikuto on the street and informs him that that Maika's egg may be the Embryo, but if it is not, Ikuto will need to clean up.

Amu takes her little sister, Ami, with her to a guardian meeting. While the Guardians hold their meeting, the Guardian Characters play with Ami and find a treasure map to a magical egg protected by a dragon.

Amu encounters Misaki Watarai, an energetic girl who is also in love with Tadase. After Saaya Yamabuki, head of Tadase's fan club, chides Misaki for Misaki's energetic personality and misunderstanding Tadase's conversation with Nadeshiko, Misaki becomes heartbroken and Nikaidou extracts Misaki's egg, but it hatches into an X Character.

Nadeshiko invites Amu to a sleep over so that the two can get to know each other better. But in order to keep Ami home, Amu makes up a story about the Seven Mysteries of the Fujisaki house. As Amu arrives at Nadeshiko's home, she begins to believe her own story. Amu and Nadeshiko enjoy their time together, but after Amu takes her bath, she gets lost inside the house. Meanwhile, the Guardian Characters chase a mouse and the ruckus they make terrifies Amu. At night, Amu attempts to sneak out, but she gets lost again. Amu comes across the dance hall where Nadeshiko is practicing for an upcoming performance and Amu thinks that she has failed as a friend for being selfish. However, the housekeeper informs Amu that this was not true. The next morning, Amu is happy that her first sleepover was with Nadeshiko.

Ami wants to decorate a Christmas tree with Amu, so after school, Amu and the Guardians shop for decorations. As the group leaves the store, Yoru steals Su's decoration and Su is separated from the rest of the group. Amu, Ran, and Miki search for Su, but eventually call it a night. Meanwhile, Su befriends a white shaggy puppy who is also lost. The next day, Amu and the Guardians search for Su. Su and the puppy come across an X Egg and the two chase after it. However, Ikuto catches the egg and is about to break before Su prevents him by taking the egg. Utau Hoshina interrupts the confrontation and uses a Character Change to take the egg back from Su. But before Utau can break it, Amu arrives. Amu does a Character Transformation with Su, becoming Amulet Clover and purifies the egg.

The Guardians go to a winter training camp and stay with Kukai's grandfather, who is the priest at a temple near a ski resort. The Guardians enter a snow-sculpting contest, each building a part of a castle. However, Amu becomes discouraged with her gate. When Amu asks Miki to do a Character Change, Miki refuses. On the way back to the temple, Amu asks Tadase about the person he said he already liked when he rejected her. Tadase explains that he was referring to his family's dog. Nevertheless, Tadase confesses that he has come to like Amu's alter ego, Amulet Heart. That night, Amu becomes depressed that Tadase likes Amulet Heart, but that Amulet Heart is not her. Ran reminds Amu that Amulet Heart is Amu's would-be self and that Amulet Heart exists within Amu. Amu then becomes determined to work towards becoming her would-be selves.

Amu goes shopping with Nadeshiko and Yaya for a Christmas party. When Amu sees a music video by Utau, Yaya informs Amu that Utau is a new idol singer. Elsewhere, Utau is practicing her performance, but when she becomes disheartened, her manager, Yukari Sanjo, brings up Ikuto. Utau is then determined to work harder. As Amu hurriedly runs home, she comes to a park where different groups are performing music. Amu hears a sorrowful melody and when she follows it, she discovers that it is Ikuto playing his violin. After the Guardian's Christmas party the next day, Amu returns home. However, the Guardian Characters feel the presence of X Eggs. They return to the park and find that everyone's eggs have been extracted en masse and have turn into X Eggs. In the middle of them stood Ikuto who disappears in a burst of wind along with the eggs.