Enter Heroes of Time/Space!

Prologue

Once there was a world devised by an ancient and nigh omnipotent evil. It was named after him; this evil was called Orochi and the world was Orochi no Sekai, "Orochi World". That was many centuries ago, and that world had fallen a part. Mankind combated it with their combined might and cunning, and afterward despite having been resurrected, the evil was defeated once more. It didn't take long for the will of the world itself to serve as its own demise. From afar and up-close Mystics from the Heavens above had been watching and even helping the Humans in their struggle. When the time came that they'd be forced back into their respective timelines, it was the Mystics who made it happen.

Despite having been returned to their lives, lacking all memory of past events in Orochi's world... They weren't safe still. Somehow, the late Orochi's armies found their way to various timelines and dimensions, destroying them one by one in search of the "Serpent-Child", a reincarnation of Orochi himself. The Humans took a great deal of damage no matter where they came from and at what time period. The Mystics had realized that they were too late, but one Mystic prone to helping Humans like she had done once already, Kaguya, knew of one dimension that would serve as their final bastion... A place the Mystics would call "Otoko no Sekai" or "World of Man". Using her powers over time/space she rescued the surviving Humans, and brought them to this alternate dimension.

The Mystic Army promised the Humans safety in Otoko no Sekai, what Humans fancied calling "Earth-02". Nonetheless, the Demon Army remained rampant across varying dimensions and times. In only a couple of centuries, Humans were able to construct a variety of castles, towns and otherwise and many among them venerated the Mystic generals/officers as deities and saints for having saved their entire species.

Unfortunately, peace didn't last long. In a world ruled by Humans, no matter the time or place, war always sparked. And various factions developed like they've done so many times in the past. These factions evolved into Kingdoms and powerful Clans resulting in many different monarchs and warlords being placed at odds against one another.

While man was infighting, the Mystics were preparing for the arrival of the Demon Army. They knew all too well, that this bastion was what it was. And time didn't pass for Mystics as slowly as it did for Humans. When the Demon Army inevitably arrived using whatever magic and technology was at their disposal, it was thanks to the Mystics preparations that the varying faction of Mankind were able to hold on to their territories on Earth-02.

Though man held on to their territories, the Demon Army still posed a threat. The war had just begun, and how would Mankind ever hope of combating this Demon Army if they weren't willing to stop combating themselves? All the while, the Mystics knew they would need Man's aid in order to vanquish this new foe, and the only way they knew to make their presence known was to become a part of the fight itself.

In a land wrought with hardship, will Man succeed? Or this time, will the Demons prevail after finding their almighty leader?