Based on the provided sources, the character aligns with the antagonist **Guwaru the Ziarc** (also romanized as Jaku). He is a powerful demon noble within the Underworld and brother-in-law to its ruler, King Aleph. Guwaru actively opposes Aleph's rule, driven by a desire to seize control of the Underworld for himself. His core motivation stems from vengeance against humanity for the ancient sealing of the demon kingdom 63,000 years prior; he aims to shatter the magical barrier confining the demons and conquer Earth.

In a pivotal struggle against King Aleph, Guwaru banishes the monarch and fractures the island of Usontō into seven separate islands, demonstrating both his ambition and destructive power. He consistently employs deception and manipulation as tactics, reinforcing his characterization as a shrewd and dangerous foe.

Guwaru is aided by his son, Kowaru the Ziarc, in schemes to steal the magical turban worn by the protagonist Hat, possession of which would secure Guwaru's dominance. Their plans often involve deploying biomechanical Petamo Beasts and henchmen like the floating servant Dogu. Despite setbacks, including the resurgence of the legendary hero Magical Hat's powers within Hat, Guwaru persists as a persistent threat driving the central conflict.

He functions as a consistent antagonist embodying the conflict between the Underworld's malign forces and those seeking balance.