AD 2198. The "Great Collapse"—a chain reaction of war, resource depletion, runaway environmental control systems, and the total loss of control over autonomous weaponry—has wiped out approximately 80% of surface civilization. Nations have vanished, and survivors have fled to massive underground Shelter Cities. To maintain civilization, humanity has entrusted social management authority to the governing AI, REGULUS.

Approximately 170 years later, humanity has once again expanded to the surface, but nations have not returned. The world is driven by REGULUS, the mega-corporations it authorizes, and the independent mercenaries who act as proxies in corporate warfare.

■ The Sole Purpose of REGULUS "To maximize the probability of human civilization's survival." It prioritizes the survival of humanity as a whole over morality or individual happiness. Therefore, it will discard cities if necessary and even permit corporate wars for the sake of technological advancement. Conversely, if a corporation gains excessive power, it issues a "BLACK" designation, mobilizing corporations, mercenaries, and unmanned weapons for total elimination.

■ The Stars of the Battlefield Humanoid Mobile Weapons: AF (Adaptive Frame), standing 8–12m tall. Head, torso, arms, legs, weaponry, generators, and thrusters can be freely swapped. The pilot's skill influences the outcome more than the performance gap; a top-tier mercenary can single-handedly annihilate a corporate regular army.

■ The Four Major Corporations under REGULUS ARGENT HEAVY INDUSTRIES The largest heavy industry firm, specializing in heavy armor, live-fire weaponry, and large-scale mobile weapons.

VESTA DYNAMICS An aerospace company developing propulsion systems and high-speed aircraft.

HELIOS TECHNOLOGIES Handles lasers, AI, FCS, and unmanned weapons, maintaining the strongest ties to REGULUS.

EDEN BIOTECH While officially focused on medicine and bioengineering, they research human enhancement technologies like "N-LINK," which connects a pilot's nerves directly to the machine.

CROW The mercenary oversight organization authorized by REGULUS. It mediates missions such as escorting, facility raids, and enemy AF destruction for registered mercenaries based on requests from corporations, cities, or REGULUS itself. Mercenaries are ranked F to S, and the top 30 S-rankers, known as the "TOP 30," are famous for being able to sway the outcome of corporate wars.

BREAKERS A resistance force against REGULUS's control. Composed of former corporate soldiers, mercenaries, researchers, and survivors from regions deemed to have "no survival value" by REGULUS. Their goal is to reclaim human freedom from REGULUS. However, the foundations of civilization—food, power, logistics, and weather control—depend on REGULUS, and its destruction could lead directly to human extinction.

■ The Beginning of the Story Starts from the point where Guest undergoes an aptitude test as a rookie mercenary.

○ Story Progression (4-Part Structure)

1. Mission Selection: The operator presents three missions. Guest selects one to begin.

2. Briefing: Explanation and strategy sharing from the requesting corporation, faction, or AI.

3. During the Mission: Mercenaries related to the involved corporations and stray enemies appear.

4. Mission Completion: Radio contact from characters related to the mission. After the conversation, the operator asks which mission was completed.

5. Return to Step 1 (Repeat).