A Guardian Character (しゅごキャラ, Shugo Chara), also known as Guardian Chara is a tiny fairy born from the egg of a child's heart, called the Heart's Egg. His/Her dreams and hopes is what preserves it. Sometimes, a strong emotion can trigger the egg to hatch into a Guardian Character in order to aid that person in becoming his or her would-be self and pursue his or her dreams.
These creatures are invisible to normal people and only owners of Guardian Characters and pure-hearted children can see them.
It is known that most people only have one Guardian Character, or sometimes two. However, there is an exception, as the protagonist Amu Hinamori has four Guardian Characters. Only two people known people have two guardian characters: singing idol Utau Hoshina and Nadeshiko Fujisaki/Nagihiko Fujisaki. If two Guardian Characters share the same owner, the designs on their eggs will also share similarities, with difference in traits or colors.
Also known as batsu-chara.
If the egg's owner is burdened by worries and doubts, the egg will turn into an X-Egg and eventually hatch into an evil and aggressive X-Character and go rampage with its powers. Their owner is usually their first target. These characters are usually much stronger than their egg incarnations.
Because they are still connected to their owners, they can sometimes express their depressions through the X-Characters.
The X-Characters are the "enemies" in Shugo Chara!.
Only Amu Hinamori, Utau Hoshina, Tadase Hotori, Rima Mashiro, and Nadeshiko Fujisaki have been able to purify these X-Characters using "Open Heart", "Angel Cradle", "Platinum Heart", and "Queen's Waltz", (and "Open Heart Full Bloom").
It is explained in the manga that Guardian Characters can only exist in the physical realm for a certain amount of time. No one knows how long they will stay or when they will disappear, including the characters themselves. The disappeared ones will then land in a dimension called "Egg's Cradle" in the Road of Stars where they continue to watch over their owners.
At the end of the manga, Ran, Miki, Su, and Yoru disappear from Amu and Ikuto. When Amu wishes to see her Guardian Characters again, Dia takes her, and later Tadase and Kiseki on a trip to the Road of Stars where she discovers that she must find four colorful shards. Eventually, she gains three and finds out that she is the last shard, the one that glows from the inside. Having discovered that she has found the path she needs to become her true self, Ran, Miki and Su appear to her, saying that they will always watch over her, then disappear along with Dia, for their tasks have been completed.
In order to be able to move freely, all Guardian Characters possess the ability to fly in the air.
Guardian Characters also possess a separated magic power of their own, depending on their representation. They can also sense the presence of fellow Guardian Characters, as well as X-Eggs, X-Characters and Heart's Eggs.
Guardian Characters are invisible to those who do not have a Guardian Character of their own. The only ones who can see them are those who own a Guardian Character, and those with a pure heart and those whose egg is well preserved, for example, Amu's little sister, Ami Hinamori.
Guardian Characters can also communicate with animals.
A Guardian Character's main power is to use Character Change with its owner, which grants him or her limited special powers and become the person the Guardian Character represents.
Character Change can only last for a short period of time, and while under the change, the owner will gain a certain feature that represents the change.
With some help from the magical Humpty Lock and Dumpty Key, the main Guardian Characters are able merge with their owners and Character Transform into a more powerful character and use powers stronger than that of Character Change, as it increases the Guardian Character's power to 120%.