Forced to protect a sinful woman thrust into the world of unseen beings after being rendered will-less, the senior guide angel Aaron slowly succumbs to darkness to save her soul from his rival and the shadows. Yet the true danger lies in a mysterious rock star who will use Aaron's tragic fall for his own ascension, and in the forbidden bond the angel forms with the sinner he protects.

SYNOPSIS:

Humanity lives amidst the silent war of a guiding angel and a guiding demon whispering to them from birth. However, this ancient order is shattered by the emergence of the "Will-less." These cursed humans, whose guides have been killed by an external intervention, can see the spiritual world with their bare eyes and corrupt every sacred entity they touch.

Aaron, one of heaven's purest guides, falls onto the radar of a banished entity known in the human world as the charismatic rock star Vesper during a routine assignment. To regain his lost power, Vesper devises a dark plan. He kills the human Aaron is sworn to protect, creating a massive void in the system. In the second phase of his plan, he slaughters the guides of a sinful woman named Yoo Ri, transforming her into a "Will-less" and ensuring she becomes Aaron's new assignment.

To resolve this anomaly, the Temple of Fate assigns the senior guiding angel Aaron and his earthly rival, the senior guiding demon Harvey. In this forced alliance stretching from the neutral towers of Purgatory to the neon-lit streets of Earth, an angel and a demon must try to save Yoo Ri from Vesper's clutches. However, as the forbidden bond deepens between Aaron and the woman he must protect, he realizes his sacred essence is slowly evolving into darkness...