A reincarnated king, raised as a poor fisherman's son and secretly trained by a great wizard, joins a knightly trial to rescue his kidnapped sister. Wielding a rusted sword, he shows immense power but faces constant doubt and persecution for his lowly birth. When he draws the legendary sword to prove his true identity, the usurper king forms a blood pact with a dragon to destroy him and the loyal knights.
At the critical moment, the wizard sacrifices his life to retrieve a sacred blade, awakening the king's sealed memories and power. The returned king slays the dragon's spirit and ends the usurper's reign. In the end, he chooses to guard the dragon seal in the north, entrusting his crown and kingdom to his sister—fulfilling both his royal duty and his bond of blood.
