The Gene Lock, a mysterious and revolutionary technology that enhances human capabilities in speed, strength, and senses to unprecedented levels. Those who successfully unlock their Gene Lock become "agents" of the new era, with the most outstanding among them known as "Gun Gods." A fierce struggle ensues over this new weapon, leading to the establishment of academies to train agents. As experiments break through and are applied, coupled with coercion from a mysterious race, the world is gradually plunged into the quagmire of war...

After the war ends, the mysterious race vanishes, and the agents and Gun Gods become unverifiable urban legends. The two remaining major agent organizations, "Deep Sea" and "Wild Serpent," relocate their bases to the seabed and underground, respectively, maintaining a secluded existence. However, beneath this peaceful facade, danger lurks everywhere.