A sister with a legendary sword hunts the empire that destroyed everything she had, while her enslaved childhood friend builds weapons on the other side of a war he never chose. The mechanical fox spirit isn't just power, it's proof that lost things can be found again, even when they're bound to someone else's hands. This show costs you thirteen episodes to watch two people separated by empire finally move toward each other.

Two sisters, Yin and Ning, have roamed the land together since the Taibai Empire destroyed their village. When Yin happens upon a legendary sword, it gives her remarkable fighting skill and lets her call forth Yun, a mystical mechanical fox spirit sworn to battle at her side. Their childhood friend Zhao, meanwhile, lives as a slave of the Taibai ruler and relies on his talent for tinkering and invention to survive the Empire's demands. He soon befriends a mysterious young girl who may wield considerable power within the Empire. As Zhao and the Fu sisters are drawn further into the Empire's fight for dominance, the growing resistance armies need every bit of magic and strength they have to change the course of the war. The story is an action fantasy adventure adapted from a Taiwanese PC role-playing game series.