Dragon Quest Saga: Emblem of Roto ~To the Children Who Inherit the Emblem~

5 years ago, in an event known as ‘The Day of Loss’, magic ceased to function. In the underground land of Alefgard, the people of the kingdom of Radatome vanished in a single night. The only survivors are Aros, the prince of the kingdom, and A-Kagi, a member of a group of bandits known as the Band of the Hawks, who infiltrated the castle that night to commit a robbery.
Aros, who becomes an amnesiac due to trauma, is raised in the care of A-Kagi and the Band of the Hawks. Years later, events lead him to depart from the Hawks and begin seeking out the truth behind "the Day of Loss" – as well as the whereabouts of his missing twin sister, who appears to be stealing sacred crystal orbs on the orders of a young boy who calls himself "Lamia."
Meanwhile, the companions of the hero Arus have been systematically eliminated by unknown parties…