From the introduction: The year is 2205. A group of Historical Revisionists have been trying to change history for unknown reasons, only citing a vague benefit to all this. Summoning a total of 840,000,000 troops from the future to do battle to change the course of history, their army numbers far more than the combined population of Japan. The Government of Time opposes this change, but in the face of overwhelming numbers, it would seem hopeless to stop The Revisionists and their forces, the Time Retrograde Army. But the Government of Time has an advantage the Revisionists don’t. The Saniwa, or Sages, that work for the Government, have a special magic art. They can awaken the sleeping hearts of powerful items, like weapons, and give them the power to fight on their own. To bring in the personifications of tremendously powerful techniques and spirits. They are called the Touken Danshi, or “sword men.” ...Or they can be women, if that’s what you prefer.