

The alien bugs invaded, and humanity retreated to the "Ark" mobile fortress. Four years ago, hero Kevin piloted the mech "Silver Scar" to defeat the swarm, but retired after his entire squad fell. When the bugs returned, Kevin reapplied—only to show 0% compatibility. Spy Marshal Sam framed him for treason, sentenced him to death, and sent his mech to the scrapyard. As the swarm breached the gates and Kevin faced execution, "Silver Scar" self-activated, rescued him, and synced at 100%. Kevin repelled the swarm, and the whole city witnessed the war god's return.

As the Monster Age arrived and special abilities awakened, what awaited humanity was the end of the world. At the brink of the apocalypse, Frank Channing was sent back in time to the second year of the Monster Age. There, he awakened the Infinite Devouring System, allowing him to gain growth points by hunting the monsters. Along with it came a mysterious serpent-shaped mark on his arm. It could transform him into a powerful serpentine creature capable of wielding the very forces of the monster—seemingly tied to the secrets of the Blood Moon. From the system, Frank learned that he carried the mission of saving the world.