Events leading up to warIt all begun with the discovery of the Susanoo Unit, which allowed humanity to detect the Master Unit within the Boundary. It was a being of immense power, possessing the ability to activate Event Interferences and capable of affecting space-time, in other words, a "god". However, after being observed through many points of view, it was realized that it was actually a creation and that it could be controlled like an object. The Takamagahara System was created in order to control its power and system, however it was flawed. While its duplicated system was capable of intervention that "rewound" the flow of time, it couldn't intervene upon the "possibilities" that compose the world, in other words, it was incapable of altering the "events". In order to obtain the missing component (the power to change "possibility" into reality – the Blue) and complete the system, many experiments were performed in order to contact the Master Unit. As the Master Unit responded only to objects with a human form, the Prime Fields were made. The first one, later on dubbed as The Origin, managed to make contact with the Master Unit, becoming its "eye" and obtaining the power of an Observer. Along with the power of the "eye", the Prime Fields gained "souls" and self-awareness. Fearing that the will of mere "dolls" could alter the world, humanity, upon the advice of Clavis Alucard, created the Anti-Observer Armament, Sealed Armament: Izayoi and destroyed their "eyes", afterwards throwing them into the Boundary. Among those thrown into the Boundary was the first Prime Field, which managed to make contact with the Master Unit once again.
Humanity's fears grew even larger than before. They feared what could Origin, who now wielded the power of a "God", do to them for the atrocities and experiments they committed against her and her "sisters", thus humanity decide to perform total genocide upon them and the Prime Fields resisted in self-defense. However, the Prime Fields, along with the first one, all had the same "dream", they wished for their "souls" to be recognized as "individuals", as well they themselves seen as humans and be able to live a normal life. Yet, humans couldn't accept them as such, as Prime Fields had far superior physical abilities than them and the Origin even wielded "power of god", not to mention that humans couldn't remove their preconception that as human creations, they could be nothing more than "dolls".
The Prime Fields were more durable and had superior combat abilities than humans, what's more the first Prime Field had the power of Event Interference. On the other hand, humans were more numerous and, thanks to Clavis's advice, already had prepared special equipment that wasn't affected by Event Interference, the Izayoi. The war was brutal and humanity, thanks to Izayoi, was able to confront their enemy, however, it wasn't capable of neutralizing Prime Fields and humanity had started reaching its limit. They decided to use a "certain something" to mass-produce a self-observing weapon of mass destruction, basing it off the technique used in creation of Izayoi, it was later known as the Black Beast.The Black Beast didn't discriminate between friend and foe, and simply devoured humans, Prime Fields, and everything it could alike, making a world with nothing left, a world of death. Thus the world had ended, however, this was in accordance with humanity's plan, as all they needed was to win. As long as they could obtain the Blue and complete the Takamagahara System, they would be able to "rebuild" everything and prevent the creation of Prime Fields, while still having the "power of god" in their grasp.