Leon Walker, a brilliant but burnt-out modern-day genius, meets his end in a bizarre accident courtesy of the legendary Truck-Kun. Yet death proves merely a gateway. He awakens in Galvia, his consciousness inhabiting the formidable frame of Duke Leon Moonwalker—one of three Grand Dukes commanding the Moonstone Kingdom, a strategically vital realm within the greater continent. As Leon grapples with his unfamiliar surroundings, an enigmatic voice echoes through his mind: "Supreme Spouse System Activated."