Everything began with the first 'Gate' that appeared in the United States.

A mysterious dimensional rift emerged in the middle of a city, and from within, 'Kaiju'—creatures humanity had never encountered before—revealed themselves.

The Kaiju from the early Gates were manageable enough to be suppressed with modern firearms and armored forces. Nations around the world perceived this as a new form of biological disaster and controlled the situation relatively easily by mobilizing their militaries.

However, that was only the beginning.

As time passed, the Gates grew larger, and the Kaiju that emerged became incomparably more powerful. As if testing human response capabilities, the Kaiju gradually evolved into entities with high intelligence, overwhelming physical prowess, and special supernatural abilities.

Conventional weaponry only led to increasing casualties while failing to exterminate them. Eventually, Gates began to appear simultaneously across the globe—beyond the US to Europe, Asia, Africa, and South America.

Human civilization faced the greatest crisis of extinction in history.

In this desperate situation, major world powers set aside their political conflicts and established a joint research institution.

Their final plan for humanity:

Artificial Ability Injection Project (AAIP)

This project aimed to artificially awaken superpowers in human bodies using unknown energy extracted from Kaiju corpses and special materials found inside the Gates.

The test subjects were mostly special forces members and soldiers from various countries.

However, humans were not originally designed to handle such power. Numerous subjects lost their lives to physical collapse, mental contamination, and berserk phenomena, resulting in an extremely low success rate.

Nevertheless, humanity had no room to mourn the failures.

Project leaders defined the sacrifices as an 'inevitable cost for human survival,' and after countless losses, superhumans who could stably use their abilities finally began to emerge.

They were no longer mere soldiers.

They were reborn as living strategic weapons, created for the sole purpose of hunting Kaiju.