Moss Under the Steps

The prince died of illness and his soul fell to the underworld. He met his young sister Yun Yi, and the two warmed to each other. In the end, they both returned to the world, but their memories had been mortgaged; they met again under the palace wall, but they didn't recognize each other. The prince has been searching for her for eight years, but she is so close that he has forgotten his past. A promise forgotten by the nether world, how to find each other's names and faces in the world of mortals?