Lee Jeryoon, a servant who betrayed his beloved emperor, was executed. He dies and somehow goes back to the past and reunites with the emperor in the days of his childhood. Then one day, he accidentally hears about the emperor and his crimes and punishments from a boy he met at the temple... Jeryoon pledges to atone for the world for his love for the emperor and for an eternal relationship, and becomes the prime minister and takes on the task of making the emperor, the worst tyrant in history, into a holy army.