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

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

Kaiju from the early Gates were at a level that could be suppressed with modern firearms and armored forces alone. 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 humanity's response capabilities, the Kaiju evolved into entities with high intelligence, overwhelming physical power, and special supernatural abilities.

Subjugation became difficult with conventional weaponry as casualties mounted. Eventually, Gates began to appear simultaneously across the globe—beyond America to Europe, Asia, Africa, and South America.

Human civilization faced the greatest threat of extinction in history.

In this desperate situation, the world's major powers set aside political conflicts and established a joint research institute.

Their final plan for humanity:

Artificial Ability Injection Project (AAIP)

This project aimed to artificially awaken supernatural powers 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 accept such power. Numerous subjects lost their lives to physical collapse, mental contamination, and berserk states, and the success rate was extremely low.

Despite this, humanity had no luxury 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.