Ja, once a worn-out Japanese salaryman, wakes from a fatal car accident in another world as a colossal evil dragon, beyond anything a demon king or a hero could match. He settles into a lazy, peaceful life deep in a forest alongside a clan of devoted slimes, until the demon king's subordinates hear of his strength and turn on his home. With the slimes he had come to care for killed, the dragon leaves his quiet retreat and sets out across the world in a human form.