Drowned in loneliness, emptiness, darkness. Lost in slaughter in pursuit of revenge. Longing for love, Liam dies shortly after completing his life's mission of avenging his murdered family. Once a young orphan, now the King of Assassins, hailed as the Dark Demon, the monster under the villains' beds, finally earns his rest.

However, fate has a different plan for him. Due to a timely intervention, Liam is reincarnated into a magic world, born in a family surrounded by love. Struggling to balance his dark side with his identity of a child, Liam, now Arthur, swears to do everything necessary to protect his family this time.

Once again, the world will feel the blade of the Demon, this time to protect what belongs to him, driven by the warmth of his new family.

Follow Arthur and his beloved companions on their journey of adventure and growth to power, watch him become a Demon God who will raze the world to the ground to protect his loved ones. In a world where the strong prey on the weak, only a true monster can make them feel fear.