[Image: Square Enix | Disney]
Pop star Utada Hikaru has become synonymous with Kingdom Hearts. It wouldn't be a main entry in the series without her music.
Utada Hikaru recorded songs for Kingdom Hearts and Kingdom Hearts II. She's back for KHIII with a track called "Chikai" (誓い), which means "oath" or "vow."
And here is the English language version, which is called "Don't Think Twice."
This isn't a full version of the theme, but it should give you an idea of how it sounds.