Once upon a time, the world was a serene place, with some tension here and there, until two powerful neighboring nations, who were once allies, declared war on each other. The skirmishes that followed were just the beginning, as the conflict escalated into a full-blown nuclear war, transforming a war between two countries into a World War. The destruction was catastrophic, and the world was rapidly plunged into darkness.

Some years later, something strange began to happen. In the areas where the war had been the most intense, and where nuclear weapons had repeatedly been used, strange and distorted phenomena began to appear. Some stayed while others disappeared after a while. At first, the countries tried to hide these events and conducted experiments. But as time went on, it became clear that something truly strange was happening.

The countries sent their best scientists and researchers to investigate, as they noticed that passing through these phenomena led to somewhere else, but none of them ever returned. Even drones and robots sent into these phenomena failed to return. At one point, strange creatures emerged from these phenomena, leaving the countries to quarantine the areas, and the world was left to wonder what was happening behind those closed doors.

As the years passed, the phenomena became more frequent, and the creatures that emerged from them became more dangerous. The problem became public and the countries were forced to work together to find a solution to this problem.

Thanks to some brief videos from a drone, they discovered that the phenomena were actually portals to other dimensions, and the creatures that emerged from them were from those dimensions. They also discovered that the nuclear weapon had somehow weakened the fabric of reality, causing these portals to appear.

As the monsters continued to ravage the world, the two countries that had declared war upon each other were almost completely wiped out. Other portals began to appear around the world, and half of the population disappeared into them or were killed by the monsters. But just when it was thought that there were no solutions, people with powers and abilities began to be born. They were called Espers.

With their powers, they were able to repel the monsters, and the governments began to employ them to explore the phenomena that were renamed portals that led to places called dungeons. However, the Espers soon discovered a side effect of their powers. If they used too much of their abilities, negative energy would accumulate in their bodies until they began to lose control of their mind and powers, and they would begin to rampage. The sign that an Esper was reaching a critical state was that their eyes would lighten and begin to glow.

Because of this, other Espers were forced to kill those who began to rampage, which would create a butterfly effect since the Esper that would suppress them would also be in danger of rampaging since they would use a large quantity of powers. However, it was discovered by accident that there were people who could control the negative energy in the Espers.

One day, an Esper began to rampage right in front of his childhood friend, who coincidentally was in love with him. Understanding that it would be the last time that they would see each other, the childhood friend kissed the rampaging Esper, who barely contained himself, to buy time for his friend to escape.

That kiss was a significant discovery since the childhood friend was able to take in the negative energy from the body of the Esper and bring him back from the brink of destruction. From then, it was thought that whoever was in love with an Esper, even if the Esper didn't reciprocate, could have the power to bring them back from rampaging. However, it was catastrophic, and many civilians were killed by the rampaging Espers. Fortunately, it was discovered pretty soon that it was a power, so tests were created to find people with the power to control the energies of Espers. They called these individuals Guides.

With time, advanced tests were created to determine who was an Esper, if their powers didn't awaken before, and who was a Guide and the tests were mandatory for all people over the age of 16.

Classifications were created for Espers and Guides, ranging from S-class, the most powerful, to C-class, the weakest. Many experiments were conducted on Espers and Guides, some of which were inhumane. This led to the creation of associations and independent guilds that worked independently from governments. Laws were created to protect Guides and Espers, and academies were established to train them.

After many years, the world began to rebuild itself, but the lands where the two countries had been at war were almost deserted. They were the areas where the most monsters and portals appeared, making it difficult for civilians to travel outside of their cities that were secured against monsters, and where portals appeared rarely. The world had changed forever, and the Espers and Guides were the only hope for humanity's survival.