Many years ago, in Feudal Japan, a brutal war was waged. Two factions fought desperately, serving their mysterious leaders, who each claimed to be a god. Though close to the truth, they were both indeed mortal, possessing only the power to kill anyone they met, often in mysterious ways.

And while this war was fought in the human realm, another was fought in the realm of true gods, the shinigami. The war between the shinigami had been ongoing now for close to a thousand years, much longer than it's human counterpart for which it was responsible.

It began about a millennium earlier, when the Shinigami King had decided to create the notes.

Since the beginning of time, shinigami had been given the power to freely control the death of humans, taking it as their sworn duty to eliminate corrupt humans, and create a peaceful world for the righteous. Even the Shinigami realm itself had prospered.

But then it all changed. A lone shinigami had traveled to the human world, and after spending years there, had it's sense of justice rreplaced by greed. It decided that it would rule the human world all itself, and remained there, calling other shinigami to join it's new world.

This was an obvious problem, one the Shinigami King had never encountered before, and that he needed to end. Unable to leave the Shinigami realm himself, and wanting to avoid conflict, he came up with a plan to stop the rogue shinigami from killing, as well as to place rules on how any and all Shinigami (besides himself) were allowed to kill.

And so, he created the Death Notes, delegating all the shinigami's power into them. Initially, the plan worked well. The rogue shinigami were stopped, while the ones remaining in the Shinigami realm had received their notes from the king, and were continuing judgment.

But it wasn't over yet. Angered at the loss of their power, the rogue shinigami returned from the human realm, demanding to receive their notes from the king. He of course refused, and killed the original corrupted shinigami. The rest fled, before regrouping, and declaring war on the still righteous shinigami.

Thus began the great war of the Shinigami.

Before the war, the shinigami realm had actually been a peaceful, beautiful place...but the war destroyed all that, and eventually, the greed and hatred of the corrupt shinigami affected the realm itself, as well as the rest of the shinigami, and even the King. They were no longer righteous, and few took any time to eliminate humans, instead concentrating on the war.

The losses were high, considering that few shinigami had ever died before this point. At one point, the King was forced to begin creating new Shinigami, in order to ensure that they didn't die out all together. Eventually they forgot why they were even fighting in the first place, yet continued anyways. And then finally, nearly a thousand years later, the end seemed near, and the two remaining rogue shinigami fled back into the human realm with their Death Notes.

Corrupted, and no longer caring about humankind, the King and the rest of the 'righteous' shinigami decided not to pursue, and the King, in order to ensure that they did something at least resembling their original job, made it so that that shinigami had a limited life-span that could only be extended by killing humans, and taking theirs.

Unfortunately, the war wasn't quite over yet...