"Code Age" is a manga series set in a dystopian future where humanity faces extinction due to environmental collapse and the emergence of monstrous creatures known as "Wanderers." The world is divided into isolated city-states, each governed by a unique system of survival. The central narrative revolves around a young protagonist, Arim, who lives in the city of Neo-Ark. Neo-Ark is a technologically advanced society that relies on a mysterious energy source called "Code," which powers their defenses against the Wanderers. However, the Code is finite, and its depletion threatens the city's survival.

Arim, a skilled but disillusioned Code engineer, discovers a hidden truth about the origins of the Wanderers and the Code. The Wanderers are revealed to be former humans transformed by a catastrophic event tied to the misuse of Code technology. This revelation sets Arim on a journey to uncover the full extent of humanity's past mistakes and find a way to restore balance to the world. Along the way, Arim encounters a diverse cast of characters, including Lina, a rogue scavenger with a personal vendetta against the ruling elite, and Dr. Kael, a scientist who harbors secrets about the Code's creation.

The plot explores themes of survival, morality, and the consequences of technological advancement. As Arim delves deeper into the mysteries of the Code, he uncovers a conspiracy involving the city's leaders, who have been manipulating the population to maintain control. The story builds toward a climactic confrontation between Arim and the ruling faction, with the fate of Neo-Ark and the remaining human settlements hanging in the balance. The series concludes with a resolution that leaves room for interpretation, emphasizing the cyclical nature of human ambition and its impact on the world.