The Anthem of the Heart

Long ago, the young girl Jun Narase dreamed of one day attending a ball at the glamorous castle on the hill. After once seeing her father driving out of that castle, she returned home to excitedly tell her mother, not realizing she'd just described her father's infidelity. And so her family falls apart, and after her father tells her it was all her fault, she falls into despair until a strange egg tells her she can save herself from further heartbreak, and maybe even find her prince on a hill. All it would take is to forever seal away her dangerous voice.

Synopsis from Anime News Network