The Ghost of Promise

Yakusoku.

Once, there was a legend of a fierce Ronin, a lost Samurai, who ventures to seek the most powerful Yokai or evil spirits within the lands and slay them without mercy. The Ronin wears a ghost mask and moves without any sound, and her blade resonate with the subtle breeze of the wind and slice through any creature foolish enough to be in her way.

Her existence was rejected amongst other Samurai of her clan, but now she's a roaming ghost. Nothing shackles her, no rules, no limitations.