Mu Yu was originally the youngest son of King Mu Kun of the Jin Dynasty in the Northern Kingdom. Later, due to the political turmoil in the Northern Kingdom, Prince Yi Mu Min, who was the fourteenth prince, seized the throne by killing his brother. In this coup, the Jin prince Mu Kun sided with the camp of the former king Muke. So after the new king Mu Min came to the throne, all the people who originally stood with Muke were exterminated. Mu Kun's wife, Shen, escaped from the secret passage with her two children. Many years later, Mu Yu learned the truth as an adult and began the road to revenge.