At some point in time, the Net Terminal Gene carriers came to a consensus to use the Netsphere to build a utopian city where they could live and create alone, separated from the rest of humanity. Governed by the Administration and protected by the Safeguard, the Netsphere grew in size and scope until its functionality reached the outer edges of the solar system.
Over time, the Carriers' city expanded across the Earth as they created new and bigger things. The Safeguard, protecting the Netsphere from intrusion, presumably destroyed the rest of humanity that did not have the gene to make room for the Carriers. Eventually, the Carriers' city covered the entirety of planet Earth.
With illness a thing of the past and hunger nonexistent, the Carriers' population increased exponentially. More room was needed in the City. The Carriers created gargantuan robots called Builders that created residential districts and skyscrapers hundreds of miles tall. Sunlight soon failed to reach the ground. The Builders constructed an enormous dome with interior lights to act as the new sun, encasing the entire City and planet inside it; the first Megastructure.
From there, the City was built upward: a new city built on top of each dome, each bigger and more impressive than the last. The Carriers lived lives of ease and comfort creating whatever they liked, as the Administration oversaw construction of everything, and the Safeguards provided law enforcement. For thousands of years, this continued, and soon, even the Moon and nearby planets were destroyed and used as building material for the City.
The Netsphere, by this point, had become another reality altogether, where humanity could travel to and back as they wished, creating their own worlds as they saw fit. Trillions upon trillions of humans living as they pleased, without a care in the world.
At some point, something happened.
A mutation occurred. Someone, somewhere, on some level of the City, was born without the Net Terminal Gene. Then another. Then another, and another, and another. An infectious mutation, source unknown, was spreading throughout the City at an impossible rate. Carriers were losing the Net Terminal Gene, and people stopped being born with them. Soon, not a single Carrier remained, and humanity was forever cut off from the Netsphere.
The Administration, unable to receive orders from anyone without a Net Terminal Gene, sat helpless as the Builders kept building new Megastructures, burying whole populations of humans alive under millions of tons of concrete and steel. Soon after, the Administration lost all control; the Builders began to create bizarre, chaotic additions to the City based on their fragmented memory of previous structures. The Safeguards, who protected the City and Netsphere from non-Carriers, began to exterminate the humans of the City, seeing them as illegal citizens.
This, too, lasted thousands of years.
Then, something happened.
The Administration, in a brief moment, took action. They sent a messenger, a soldier, to reclaim the City. Giving him a gun and a mission, they set him out to find the Net Terminal Gene, and save humanity from total annihilation.
This is where the BLAME! manga begins.