The series "Gavan Off-Duty" is a spin-off project that may or may not touch upon the everyday lives of various Galactic Federation Police members beyond what is depicted in the television series. These are their stories. We see the Gavans face trials and hardships on the job day and night, but what about when they are off duty? Little do they expect the epic events that may transpire in their downtime. This is not a record of their battles, but of the stories to be found in between.

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.