One day, Meliodas, a boy who runs an inn called 'Kankotoritei' accepts a guest by a mysterious beauty who claims to be Elizabeth wearing armor.

Soon after, the knight of the kingdom raided the inn, but Elizabeth repulsed it.

She says she is on a journey to restore peace to the kingdom, seeking the lost sword that the most powerful Holy Knight once took away with the princess.

The sword was actually a kitchen knife used by Meliodas, and it was restored to its true form in response to the power of Meliodas, who found out what he wanted to protect.Thus began Meliodas' long journey.