The air has been poisoned and the shores have been drowned. What civilization that didn't crumble has had to adapt to a world under the constant threat of warmongering monsters. Those that don't live in the floating Ark Cities must scrape by as scavengers in a world that's quickly rejecting human life.

One such scavenger is Dang Thu Mai. She and her ship, Penumbra, sail lonely coastal ruins in search of salvage. While Dang wants nothing more than to keep to herself, she is forced to contend with both rival scavengers and otherworldly menaces.