Shugo Chara! is a Japanese shōjo manga created by the manga author duo Peach-Pit. The story centers on elementary schoolgirl Amu Hinamori, whose popular exterior, referred to as "cool and spicy" by her classmates, contrasts with her introverted personality. When Amu wishes for the courage to be reborn as her would-be self, she is surprised to find three colorful eggs the next morning, which hatch into three Guardian Characters: Ran, Miki, and Su.
Peach-Pit uses Amu to explore differences between one's true self and the self that is presented to others. Like Jun Sakurada in Peach-Pit's previous work, Rozen Maiden, Amu tackles issues such as alienation and fitting in at school. Unlike most heroines in other magical girl series, Amu is neither the perfect sweetheart nor a complete klutz. Amu gets grumpy and frequently talks back to others in contrast to the polite schoolgirls that fill the genre.
Amu's Guardian Characters—Ran, Miki, Su, and later Diamond—aid her in her quest of self-discovery. Each Guardian Character represents an aspect of Amu's true self. Ran represents Amu's desire to be more honest and athletic, Miki represents Amu's desire to be more level headed and artistic, Su represents Amu's desire to be more caring and improve her domestic skills, while Diamond represents Amu's desire to shine in front of others and be a good speaker. Moreover, the Guardian Characters are more than mere mascots who help Amu learn about her true self. They can also perform a "Character Change" where Amu's personality is replaced by an entirely different one.
However, Amu is not the only one with Guardian Characters. Each of the Guardians—Tadase Hotori, Nadeshiko Fujisaki, Kukai Soma, and Yaya Yuiki—have their own Guardian Characters. Amu also encounters Ikuto Tsukiyomi and Utau Hoshina(Tsukiyomi), two siblings who also have Guardian Characters and are employed by the Easter Company to search for the Embryo.
Eventually, Nadeshiko Fujisaki and Kukai Soma leave the Guardians and are replaced by Rima Mashiro and Kairi Sanjo, respectively. Kairi later leaves and is replaced by Nagihiko Fujisaki, Nadeshiko's real identity.
Amu Hinamori (日奈森 あむ Hinamori Amu), the series' protagonist, is a student of Seiyo Elementary. Amu's classmates see her as "cool and spicy" Amu can be identified as a Tsundere (Mean and Cold to opening up to other people), but Amu's true character is 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 she expresses her shyness. However, when Amu wishes for the courage to become her would-be self, three colorful eggs appear. When they hatch, they reveal Amu's Guardian Characters: Ran, Miki, and Su.