Gomin(2004)

Gomin is an animated series set in the kingdom of Gusinakhon, where King Gosutum rules over three sons. The youngest, Gomin, possesses a rare magical artifact granted at birth that grants him extraordinary power. At just twelve years old, the young prince wields enchanted weapons with remarkable skill and fearlessness. When Gomin and his friend Musa venture to the beach, they encounter the son of Kato Naga, ruler of the underworld realm. A deadly confrontation ensues, setting off a chain of events that will test Gomin's abilities and reshape the balance between the surface kingdom and the dark forces below.