Xiao Chen, a modern special forces chief instructor, unexpectedly travels through time and becomes the frail ninth young master of the Zhenbei Prince's Estate. His father and eight elder brothers have all fallen on the battlefield. Taking advantage of their deaths, the emperor seizes military power and intends to bring all eight widowed sisters-in-law back to the capital. At this critical moment, the Old Madam orders Xiao Chen to shoulder the responsibilities of the Ninth Branch, protect the Xiao family's bloodline, and safeguard its northern territories. Facing political schemes, wavering military morale, and invading enemies, Xiao Chen uses his past life's tactical wisdom and iron-fisted methods to win over the Zhenbei Army. Together with his eight talented sisters-in-law, he breaks through one crisis after another, transforming from a frail young master despised by everyone into the mighty Prince of Zhenbei who commands the respect of the world.