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 which at first did not 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. He is also the older brother of Utau Hoshina. As the series goes on, he grows very strong feelings for Amu -- he confessed that he loves her in the same chapter Tadase did, although she believes that he is teasing her. 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. In chapter 37, Tsukasa told Ikuto he resembles his father when he yells. In chapter 38, he Character Transforms with all of Amu's Guardian Characters into Seven Seas Treasure. In the latest chapter, Ikuto calls Amu 'princess' and she replies by asking him to thank her for making him get back to normal. Ikuto swears that this time he will be the one to protect her, along with Tadase.
Yoru~
Yoru is Ikuto's cat-like Guardian Character and represents Ikuto's desire to be free like a stray cat. Yoru often goes out by himself and enjoys causing trouble for the Guardians and their Guardian Characters for fun. When Ikuto and Yoru undergo a Character Transformation, they become Black Lynx. Yoru is hysteric when Ikuto does the Death Rebel Character Transformation in chapter 31. Lately, he also can't track Ikuto, because the hypnotizing fork confuses him. Later on, when Amu and Tadase find Ikuto being controlled by Easter, Yoru takes the Dumpty Key and gives it to Amu.

is a junior high student model turned singing idol. She is actually Ikuto's younger sister, Utau Tsukiyomi (月詠 歌唄 ,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. She kissed him in episode 29. However, she eventually accepts Amu.
She was the vocalist of the indie band "Black Diamond" which is produced by her manager, Yukari Sanjo, 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.