In the fifth year of the Tianbao era, over a century into the Tang Dynasty's reign, Emperor Li Longji, weary from decades of rule, finds solace in the company of his newly appointed Yang Guifei. His focus shifts from the tedious affairs of state to the pleasures of music and dance, leading to his neglect of court duties. Meanwhile, in the spring of that same year, a newcomer arrives at the Anxi's Su Lou frontier fortress – a time traveler from the future.