Through a calculated scheme, the forces of Beiyi strike Baicheng, a vital town on the northern frontier of the Daqi Kingdom. Its guardian, Tang Yao, leads his people in a hopeless defense, but they are overwhelmed and killed. Only his second daughter, Tang Ying, lives. Worse still, her father is branded a traitor who worked with the enemy despite giving his life for his country. Tang Ying heads to the capital to take up her father's post and soon finds that nothing there is straightforward. She faces questions about Yuan Lang, the second prince who has spent decades as a hostage, and whether he has ties to Beiyi. She also faces a woman posing as her who resembles her uncannily, talk from Yao Niang about a person from another world, and strange yet familiar memories that keep surfacing. The result is a 16-episode action ONA built around a web of mysteries.