Utau Hoshina is a junior high student model turned singing idol. She is actually Ikuto's younger sister, Utau Tsukiyomi) . 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. 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. In the anime television series, Utau is voiced by Nana Mizuk.
Informations source: Wikipedia