In Hazama, the world between Heaven and Earth, conceited human souls exist in a state of purgatory. Selfish individuals who cannot see past their own delusions materialize unique "phantoms," which can look like anything from a single school to an entire city. Other unfortunate souls are drawn to lone phantoms and become trapped inside, doomed to be subsumed by the vain soul's ego.

Rock is a soldier in the Black Shooter army and her partner is the serpentine, sentient, and transforming weapon Ron. Their mission is to infiltrate phantoms and reclaim the souls at their sources, bringing them to a place where they can be purified and ultimately ascend to Heaven. However, the duo's efforts are hindered by the enigmatic Dead, another Black Shooter, who disdains helping sinners achieve salvation—instead, she consumes souls, destroying them.