During the 3000 year war in Britannia, all of the Demon Race were thought to be sealed inside the Coffin of Eternal Darkness, with the exception of Meliodas being cursed by his father, the Demon King, but what if he wasn't the only one? Enter Y/n, the third son of the Demon King and the only other demon not sealed away. 3000 years later, the brothers are viewed as traitors to the kingdom of Liones, alongside the Seven Deadly Sins, but are framed for the crime of killing the Grand Master, Zaratras.