All landmasses have been submerged beneath the ocean, and no human has seen land for generations. The sea’s ecosystem has drastically changed, giving rise to fish that consume machines. Since all remaining food and resources are now found inside these mechanical creatures, humanity must fish them to survive.

The story follows Karo, an experienced salvager who has spent years mastering the dangerous skill of capturing these ocean-dwelling monsters. He is approached by Amari, a navy officer, who requests his help with a particularly dangerous target. A gigantic mechanical monster fish named Jenga has been attacking and devouring artificial islands, threatening the last bastions of human civilization. Karo agrees to take on the mission, but his decision is not driven solely by duty or survival. He learns that Jenga contains a specific machinery part, and it is this discovery that compels him to pursue the beast.