In a floating city ruled by God, devotion is law, and identity is earned. Angelique, a devout Sister, has spent her life striving for the role of Golden Sister. But instead, she is forcibly promoted as a Silver Sister, bound to Isaiah, a reckless Seraphim warrior with the highest kill—and death—count.

Thrown into a world of combat against the deadly Malthisans, Angelique is tasked with fixing a man living in constant defiance of his own mortality. Can the two learn to live with each other when they were raised so differently?