Fairyheart.

As the only fairy child in the immortal fairy kingdom, Lala is fascinated by human children. But humans are outlawed by the wizard Aterpater, who wants to put an end to their existence by cutting a thread tying fairies to humans. Having met Bea, a grieving human girl, Lala is certain humans deserve to live and will sacrifice his fairy heart to restore the thread, saving both fairies and humans too.