Across the Jiuzhou Continent, the immortal sects flourish and are widely revered. When cracks open in the barrier between worlds, otherworldly demons slip into the major sects, hoping to seize their power from within and overturn the continent. Sword Immortal Mu Xun and his companions halt the invasion, but they fall into a demonic trap and are branded traitors. To hunt the hidden demons, Mu Xun disappears and leaves his sole son, Dongfang Hao, with his mother's family. Though he carries imperial blood, Dongfang Hao lacks spiritual roots, so his relatives treat him as mediocre and bully him. Through relentless effort he advances along the path of cultivation, protects his friends and searches for his vanished father, resolved to unite the sects and expel the invaders. The 20-episode ONA blends action, adventure and fantasy.