The heroine of the story is a 13 year old girl named Joule.
She is the first ever synthetic adept, created by Sumeragi Group in
their laboratories. Her septimal power, known as the Muse, allows her to
enhance the powers of other adepts through songs usually projected by
her alter ego, a virtual pop idol named Lumen. She is rescued from the
clutches of Sumeragi by Gunvolt, at which point the two of them begin
to live together.