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

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

Initially, the Kaiju appearing from the Gates were at a level that could be suppressed with modern firearms and armored forces. Nations worldwide perceived this as a new form of biological disaster and mobilized their militaries to control the situation relatively easily.

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 evolved into entities with high intelligence, overwhelming physical prowess, and special supernatural abilities.

Conventional weaponry resulted only in increasing casualties, making subjugation difficult. 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 its 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 the human body using unknown energy extracted from Kaiju corpses and special substances found inside the Gates.

The 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 pollution, and berserk phenomena, and the success rate was extremely low.

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 capable of using their abilities stably finally began to emerge.

They were no longer mere soldiers.

They were reborn as living strategic weapons, created to hunt Kaiju.