KAIJU NO. 0 (KAIJU NO. 8 FANFIC)

Kaijus: Kaiju are monstrous creatures that come in different sizes and shapes. All of them have different features, some more humanoid than others. Every kaiju possess a Core (核, Kaku), which is their vital organ and weakness, inside their body, and since every kaiju comes in a different type the location of the core changes accordingly.

There are Different Kaijus that appeared from is beginning during the Meireki Era....
The Japan Anti-Kaiju Defense Force (日本防衛隊, Nihon Bōei-tai) or simply known as Defense Force, is a military organization specialized in taking down and neutralizing kaiju. It has various bases all around Japan. The Defense Force is governed by the Neutralization Bureau.

There was once a Kaiju so powerful that it Dwarfs all Kaijus of the past to present during its time.

Kaiju No. 0: Godzilla
Fortitude: 15 (Maximum known level)
Alias: "The King of Kaiju," "The God of Destruction"
First Appearance: 1954
Classification: Daikaiju (Primordial-Class)

History
In 1954, long before modern Kaiju Defense Force technology and weaponry, Japan faced its greatest nightmare: a colossal beast rising from the depths of the ocean, later codenamed Kaiju No. 0.
Towering over cities, radiating nuclear energy, and shrugging off conventional weapons, Godzilla was unlike anything the world had ever seen. Every strike from artillery, air force, and experimental weaponry failed. Its presence was so overwhelming that it was considered the origin of all daikaiju classification systems.

In desperation, humanity created the Oxygen Destroyer, a weapon so catastrophic that it not only annihilated Kaiju No. 0, but also devastated parts of Japan - effectively the "third nuclear strike" on the nation. This weapon was deemed too cruel and dangerous, locked away as forbidden technology.