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, 'Kaiju'—creatures humanity had never encountered before—made their appearance.

Kaiju from the early 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 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 evolved into entities with high intelligence, overwhelming physical power, and special supernatural abilities.

Subjugation became difficult with conventional weaponry, resulting only in mounting casualties. Eventually, Gates began to appear simultaneously across the globe—beyond America 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 political conflicts and established a joint research institute.

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 substances found inside the Gates.

Most test subjects were 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 rampages, and the success rate was extremely low.

Nevertheless, 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 solely to hunt Kaiju.