Jang Yiseo, a spy from the Murim Alliance who infiltrated the Demonic Cult, was given his first and last mission. To make the notoriously unruly Seventh Young Master, Ma-oh, the Vice Cult Leader! Despite his extraordinary martial prowess, Yiseo’s potential was hindered by his frail constitution. Meanwhile, Ma-Oh, a prodigious yet unpredictable force, walked the fine line between genius and madness. As their fates intertwined, the two had to navigate treachery, power struggles, and the ever-present risk of exposure. Can Jang Yiseo make Ma-Oh rise to the rank of being second only to the Cult Leader, or will the shadows consume them first?