In ancient times, gigantic creatures called "Horned Beasts" ruled the Earth, but at some point, they were sealed away in items called "Egorgear" and disappeared from the face of the Earth. In modern times, humans have emerged that use a megaphone-shaped item called "Kakuseiki" to draw out the power of the Horned Beasts sealed in the Egorgear, and they have come to be known as "Hunters". Shout of Flame, an explorer who is well-versed in ancient scripts, makes a living by selling the artifacts he unearths. One day, he discovers a Kakuseiki and an Egorgear on an altar of an ancient ruin. Confused by this "Kakuseiki Omegahorn", which is different from the standard Kakuseiki used by modern hunters, he sets the Egorgear in place, and a gigantic beast with horns, Enkaku, appears. Seeing the qualities of a "king" in Shout, Enkaku orders to call himself, "Captain Omegahorn" and fight alongside him, leading to a battle against a diverse cast of hunters wherever they go.