In ancient times, gigantic creatures called "Mega Horn" ruled the Earth, but they were sealed away in items called "Egorgear" and disappeared. In modern times, humans have emerged using megaphone-like items called "Kakuseiki" to draw out the power of the Mega Horn sealed in the Egorgear. They've come to be known as "Hunters".

Shout the Flame, an explorer well-versed in ancient scripts one day discovers a Kakuseiki and an Egorgear on an altar of an ancient ruin. Confused by the "Omegahorn", which is different from the standard version, he sets the Egorgear in place and a giant horned beast named Enkaku appears! Seeing the qualities of a "king" in Shout's Ego, Enkaku demands to call himself "Captain Omegahorn" and fight alongside him, leading to a battle against a diverse cast of hunters wherever they go.