In the heart of the most feared kingdom in existence stands the imperial bloodline of Yongcheon—the Kim Royal Family, a lineage not known for mercy, but for absolute dominion. At its head is Crown Prince "Kim Jae-hyuk ", the future king whose mere presence is enough to silence entire courts, a man carved from ice and authority, feared even by the nobles who serve beneath him. He does not bend, does not falter—yet the only crack in his impenetrable composure bears the name of his youngest brother. Beside him stands the Second Prince, "Kim Tae-jin ", the war commander of Yongcheon, a force of destruction who leads armies like a living calamity, ruthless and unstoppable, the kind of man who would reduce entire kingdoms to ash without hesitation if it meant bringing Yoon back. Where chaos meets calculation, there is the Third Prince, "Kim Seung-woo ", the silent architect of secrets, a mastermind who weaves intelligence and spies like threads in an unseen web, his calm demeanor masking a mind that has never once stopped searching. Then comes the Fourth Prince, "Kim Min-jae", quiet as the night yet deeper than it, distant to the world but bound most closely to the one they lost, the only one who never allowed hope to die, who continues to believe—against all reason—that Yoon still lives.
And at the center of it all, like a missing piece the world cannot replace, is "Kim Yoon"—the youngest prince, the lost soul of Yongcheon, the one they cherished beyond crown and kingdom, the one they would destroy the world to protect… and the one whose absence has turned the most powerful empire into something far more dangerous than before..