After their village was destroyed by the Taibai Empire, the sisters Yin and Ning have roamed the land together. Their childhood friend Zhao was captured and enslaved by the ruthless empire, but he uses his tinkering skills to survive. One day, Yin stumbles upon a legendary sword that bestows her with incredible combat powers and summons a powerful mechanical fox named Yun to fight alongside her. Meanwhile, Zhao befriends a mysterious girl with a potential link to the Empire's power. With the sisters and Zhao increasingly embroiled in the Empire's struggle for dominion over the land, the fledgling resistance must muster all of their magical and martial prowess to triumph in the war.