Saya Kemmochi/Introduction
—Meti's Sword Manual, Kill Six Billion Demons
Long ago there was a young woman named Saya who was the youngest daughter of a daimyo's concubine in the final days of Edo Japan. Her life was planned out for her before she could understand even a single word of any explanation of what her course was to be, and one of the first things she ever came to understand was that her opinions of that predetermined path were not to be considered and that any deviation from it was to be harshly punished. Unfortunately, fate would come to decide that the thing her heart would want more than anything else would be a dramatic deviation from that plan. The love she developed for a kabuki actor who came to perform for her family was absolutely such a deviation.
To this day, Saya doesn't know how it was that her lover made the deal that that was made in order for them to both be together. She only knows that the person she loved brought her to a strange place, telling her that a bargain had been struck by which she would remain at her lover's side until one or the other's death. The being that granted them this boon honored the letter of the promise, of course, just not the spirit of it. The actor was made into an oni and Saya into a sword, to be perpetually carried at her lover's side. The two were bound together by a curse, under which her lover would live eternally and she would remain unbroken for so long the blade of her was used to claim the life of someone innocent at least once for each turning of the moon, and as long as she was never sheathed or set down without the shedding of another's blood.
The two wandered their new master's realm for longer than either of them could reckon. Saya was only aware of the world around her when she was drawn, only able to communicate through the song of her passage through the air as she was swung, and knew little more than the warmth, the comfort, the satiety, the horror of being bathed in innocent blood.
And then came a period of surcease. She doesn't know how long her lover went without drawing her, or why. She has only a vague sense that it was longer than the usual span between conflicts and then she was drawn again, in the heat of frantic battle. The events of that fight are a blur, all other memories of it overwhelmed by the pain of both her body and her heart being broken. In a single blow, she was shattered and her wielder was cut down.
No longer a useful tool she was simply discarded, tossed back into the real world. She found that it was a world that had moved on without her, as strange to her as the place she had spent those countless decades.
A world where she was, for the first time ever, free to make her own choices.