Ex-soldier Sunho lives in the Under World, with no recollection of his previous life. He does odd jobs to scrape by, until he comes across the chance of a lifetime: capture the girl who wields the light.

Ren is a spirited acrobat with a hidden magic - when her family is attacked by a humanlike demon, she releases a blast of silver light to kill the monster. Suffering a devastating loss, she now must save her beloved uncle from succumbing to a poisoned wound. Following the creature's trail, Ren's path collides with Sunho's; but he doesn't realise that she is the girl he is hunting. As the two grow closer, they soon realise that their pasts - and destinies - are more entwined than they could possibly have imagined . . .