Focusing on this new type of armament, various forces have fought fiercely and have set up colleges to cultivate special agents. With the breakthrough and application of the experiment and the coercion from the mysterious race, the world gradually fell into the mire of war. After the war ended, the mysterious race disappeared, and the agents and the gun gods became unproven urban legends. The special agents “Deep Ocean” and “Wild Snake” relocated their bases to the seafloor and underground, respectively, without disturbing each other. However, in a scene of peace, the crisis is perilous.