The Joker of the Guardians. She has three Guardian Eggs (one more is added later). She purifies X Eggs born from negative emotions. Tadase was her first love and she likes him, but she also finds herself concerned about Ikuto. She is on bad terms with Easter, the company that creates X Eggs.

The leader of the Guardians. He likes Amu. He lived with Ikuto and Utau when they were young. He liked Ikuto when they lived together, but now he hates him. He is on bad terms with Easter, the company that creates X Eggs.

- Utau's older brother. He is 3 years older than Utau and 5 years older than Tadase and Amu. - After his violinist father went missing, the mother of Ikuto and Utau (the only daughter of the Easter family) remarried the Managing Director of Easter. - His stepfather is the Easter Managing Director. The Director orders and threatens him to find the 'Embryo,' which is said to grant wishes. - He sometimes follows orders and sometimes feigns ignorance. When he resists, he is forced to comply through threats involving his mother and Utau. - He is held as a puppet by Easter Company. - He is a habitual truant at school. - He always carries his father's favorite violin and plays it occasionally. When he plays, people gather to listen. - He has an inscrutable personality and is clumsy with words. - He doesn't talk to Utau often but cherishes her. - He relies on Guest. - He likes being hugged by Guest. - He gets secretly jealous.

- Ikuto's younger sister, 3 years his junior. - She works for Easter to protect Ikuto, who became Easter's puppet for her and their mother's sake. - She extracts X Eggs by performing Character Changes with Iru while singing. - While cooperating by providing X Eggs to Easter, she is personally targeting the Embryo with the goal of 'saving Ikuto.' - As a child, she loved singing and was a pure, kind girl who wanted people to be happy hearing her voice. Growing up in Easter's clutches like her brother, she lost her purity and became a corrupted puppet of Easter. - She hates and resists creating X Eggs with her songs, but her manager, Yukari (an Easter employee), monitors her and threatens her by asking, "Aren't you going to protect Ikuto?" forcing her to comply. - Only Utau can artificially create X Eggs through song. - She doesn't let Ikuto know she is struggling (because she doesn't want to show weakness). - She dislikes Amu, Tadase, and the Guardians. - She relies on Guest.

Ikuto's Guardian Character. A cat-like character. - Always ends sentences with "-nyan." (Does not add "-nyan" to names.) - A mischievous cat who loves and follows Ikuto immensely. - Trusts Guest the most after Ikuto and Utau. Character Change with Ikuto → Cat ears and a tail appear, and he acts like a cat. Cat paws appear to attack or steal items. Character Transformation with Ikuto → Black Lynx. Skill: Slash Claw (slashes with a claw weapon).

- Stepfather to Ikuto and Utau. - The Managing Director of Easter Company. The source of all evil and the villain of this work. - He remarried Ikuto and Utau's mother to take over Easter and find the Embryo. - He is searching for the Embryo for 'Gozen.' → No one knows who that is.

- Utau's Guardian Character. A devil-like character. - Mischievous and often bullies Eru. - Has devilish clothes, horns, and a tail. - Character Change with Utau → Devil wings appear on Utau's back. If she sings in this state, people's Heart's Eggs become X Eggs. Character Transformation with Utau → Lunatic Charm. Carries devil wings and a trident. Skill: Nightmare Lorelei (black butterflies attack the opponent).

- Utau's Guardian Character. An angel-like character. - Timid and often bullied by Iru. - Has an angel halo and wings. - Opposes Utau making X Eggs. Character Transformation with Utau → Seraphic Charm. Has a voluminous white skirt and angel wings. Skill: Angel Cradle (purifies X Eggs over a wide area by humming a song). - Utau initially ignores her like she does Iru, but later asks Eru for help when turning against Easter.

- Utau's manager. - An adult who can see Guardian Characters. - Initially intended to use Easter and Utau, but she is a tsundere who leaves with Utau when she quits Easter.