Disclaimer: All DGM characters in this story belongs to Hoshino Katsura, creator of D. Gray-man.

Summary: Year xxxx, technology has advanced to new heights. Slavery is legal and human experiments flourished, bringing about modified slaves. They are made to obey their Masters, robbed of control over their own lives. But there exists a hidden organisation who aids those slaves. However, when calamity befalls, can they persevere or will they fall together with the last traces of humanity?

Prologue

Year xxxx.

Technology has advanced to new levels that were thought to be impossible a thousand years ago. The world was now filled with technology at every corner. Robots crawled through the streets in the forms of animals and humans alike. Humans have become so dependent on technology that removing them from the comfort of advanced technology would surely kill them.

Though there were still areas that had retained their historical forms, those areas were steadily being wiped out to make way for the future. Humans didn't like being stuck in the past anymore.

With advanced technology, humanity has become nothing more than a superficial appearance. Hundreds of experiments were created on their own kind, for the sake of gaining new technology. Many have died at the hands of scientists, but the world did not care because sacrifices were necessary for growth.

Besides, the current world was heavy overpopulated as it is. Killing off some humans for the greater good of science was seen as an honourable act.

One such experiment they did was the modification of humans.

Slavery has been legalised, and owning a high number of slaves shows off the wealth and prestige a person carries. But that was not enough for them. Slaves were good and all, but still, they were humans. They had the ability to think, to fight back.

It only caused endless troubles.

So the scientists began experimenting on removing a human's free will.

After countless years of trying, they finally succeeded. Slaves that were bought from the legalised shops all came with options for the Master to choose from. The Master has to decide if they wanted their newly bought slaves to be embedded with a microchip that would erase their ability to think.

Those who had a microchip placed into them are turned into beings just like robots. The only difference between an actual robot and a human-turn-robot was the human robot's smoother and more vivid displays of emotions.

Emotions were one thing that the scientists have often struggled with. They try and try, but they were never successful in completely capturing the intended emotions. Thus, human-turn-robots were highly sought after.

The years passed peacefully, though stagnant. But then, there came the need for change.

Humanity was a race that would quickly grow bored due to a lack of new exposure. So the scientists decided to try something new, something different. That is, creating humans that were half animals.

Mixing the genes of animals and humans together, modifying them to become compatible with each other.

Within ten years or so, their efforts borne fruit.

Humans with the characteristics of animals. From cat ears to tails of near extinct foxes, everything could be found. Still, there were many, many defects from this successful experiment.

Some humans are robbed of their voices, becoming mute. Some are blind, some are deaf. There were also those with extra pairs of animal ears. All those defects are either killed or sent far away to do work that no other human wanted to. For example, hard labour that the humans refused to waste their robots on.

Prices for advanced technology were sky-high, so when opportunities for free labour came, they made good use of it. It didn't matter if those defective slaves died in the process, because there were many more to take their place.

As for those perfected modified human-animal slaves, they waited to be bought, kept in a deep basement that held no windows. This was to prevent them from attempting an escape. With their genetics similar to that of animals, catching the runaways would be a pain.

It was not impossible, just that no one had the time to deal with that.

So the slaves were locked up in a place where there was barely any light, and nothing to show of the outside world. They may have heard of the outside world through stories, but stories were only stories. With no prove that it actually existed, why would they attempt something useless?

And so they waited, waited until the day came where their Masters would come and bring them out into the outside world.

Of course, in a world where technology was so advanced and slavery was legal, there were still bound to be illegal shops all around.

There were people who frequent those illegal shops with requests that were turned away from the legalised places. Such as creating a human-animal slave with two different types of breeds. Or even for crazy stunts such as mixing dangerous reptilian genes, like say, a snake.

Those illegal places thrived well, with many influential figures backing them up and helping them hide from the government. They would even aid in catching the needed animals for those experiments as well.

Sometimes, would-be Masters would kidnap people off the streets – be it male, female, or a child – that has gained their interest and send them over to be modified to their liking instead of having one created from scratch in a lab.

Missing people reports constantly flooded the government, but with corruption running rampant on the inside, it was impossible to find a lead on those missing people. Therefore, an unspoken rule was set in place.

Families of missing people had better give up the moment they realised someone close to them was kidnapped. Because even if they returned, they would never be the same. Death was the only merciful action left for them.

It was frustrating, it was painful.

But it couldn't be stopped.

And the place where these illegal shops thrived was called the Underworld.