Blame!: Denki Ryoushi Kiken Kaisou Dasshutsu Sakusen

Steel and rust. The City structure has endlessly propagated itself for so many years that the reason for such growth has long since been forgotten. Even within such a techo-dystopia, humans still exist: The Electrofishers. Driven to the brink of extinction, they are visited by a traveller—a man named Killy. But will his presence bring the Electrofishers ruination or hope … ?

(Source: Kodansha USA)