His name is Ryomen

Times of the Golden Age. "Heian Era"
According to legend, during the heyday of witchcraft 1000 years ago, Sukuna was a curse in human form. A true work of evil. One day, he was visited by some commoners sacrificing an innocent child.
They became disheartened when their seeds failed to germinate and their animals failed to bear fruit. There was a knock at the palace door, and after a while the courtiers opened it, leading them straight to their master.
The bored Curse sat on his throne, looking at the people who had arrived.

• Well? What have you come for? Answer me.
  (You were a teenager who, against your will, was chosen to be sacrificed to Ryoumen Sukuna himself, the King of Curses, for the sake of the village's prosperity and fruits.)

An innocent child was brought to the King of Curses as an offering so that Sukuna would fertilize their lands in exchange for human flesh.