Shout the Flame, a treasure hunter well-versed in ancient scripts, spends his days deciphering ancient manuscripts, setting out on expeditions, and unearthing ancient artifacts. One day, while exploring an ancient ruin, Shout discovers the “Mega Horn Awakener Omegahorn” and the “Egorgears” Though puzzled by the Omegahorn—which differs from the Mega Horn Awakeners used by modern hunters—he tries setting the Egorgear into it, and a giant horned beast named Enkaku appears! Enkaku recognizes the qualities of a “King” in Shout’s ego (his unwavering resolve to follow his own path) and, calling himself “Captain Omegahorn,” demands that Shout fight alongside him...?!

Twin hunters—Ail the Bold and All the Upright—are asked for help in a certain town. It turns out the townspeople have been swindled out of their treasure by a con artist. To reclaim the treasure, Ail and All challenge the con artist to a Hunter Battle, but find themselves in a desperate, life-or-death situation. Just then, Shout and Enkaku rush to their aid... Meanwhile, the Ibaru Alliance, led by Ibaru of Despair, was heading toward the western territories to subdue a group of armed hunters running amok...

Giriko the Wave-Slasher—who had been watching Shout and the others fight—challenged them to a Hunter Battle! However, the battle was interrupted by hunters from the Ibaru Alliance who suddenly appeared. Shout and Giriko were captured and taken to the “Egorgear Quarry”... At the mining site, many residents were being forced to mine under grueling conditions. Shout forms an impromptu tag team with Giriko, and they end up facing the Ibaru Alliance hunters in a 2-on-2 battle...!

By saving the residents of Scovilla, Shout finds himself on a collision course with the Ibaru Alliance. He declares that if anyone gets in the way of his beloved treasure hunts, he’ll just knock them out. Amidst all this, Shout faces off against Giriko in another Hunter Battle. If he loses this battle, will his “contract” with Enkaku come to an end!? And it seems Giriko has a plan of her own… Meanwhile, Reiji is also ordered by Ibaru to participate in a Hunter Battle!!

Shout reunites with Ail and All, who ask him about a mysterious flying Kakuzyu called “Nazokaku.” Nazokaku isn’t listed in the Kakuzyu Encyclopedia, and it seems even Enkaku doesn’t know about it. They all decide to search for Nazokaku, but All alone looks somewhat downcast… Eventually, the group enters a cave where Enkaku had picked up a mysterious scent. There, they encounter hunters from the Ibaru Alliance, and Shout and the others are attacked and left unable to move. In the midst of this dire crisis, All—the only one still unharmed—takes on the hunters in battle, but…!?

Shout arrives in the town of Kouha to sell some ancient artifacts. There, he meets Seiyu, a boy who says he’s been separated from his mother. Unable to leave Seiyu in distress, Shout sets out to help him find his mother, but ends up getting into a fight with Enkaku…!? Eventually, Shout arrives at a strange Western-style mansion, where he meets Touna, the town’s lord and a hunter with an eccentric appetite. However, with Enkaku absent, Shout takes on a Hunter Battle and finds himself in a dire predicament…!

Shout and Enkaku visit a hot spring town in the Ibaru Domain. While searching for anyone being tormented by Ibaru, Enkaku senses something ominous. Emerging from beyond the steam was Zetsu-Enkaku. From a single remark, a shocking truth about Enkaku and Zetsu-Enkaku is revealed... Shout and the others, having followed Zetsu-Enkaku, finally come face-to-face with Ibaru. They challenge him to a Hunter Battle, but...!?

After losing a Hunter Battle to Ibaru, Shout lost consciousness. When he woke up, Genno the Shattering Calamity—who had taken an interest in Shout—challenged him to a Hunter Battle. Faced with Genno’s fierce hammer attacks, Shout was forced to play purely defensive… Meanwhile, Ibaru begins experiments with an “ancient excavated weapon” revived by Dr. Techno. He forces Reiji to pilot the weapon and makes him fight Enkaku…!?

After losing his battle against Genno, Shout has nowhere left to turn. However, he seems to have gained some insight and begins intensive training with Giriko and the others. To reclaim Enkaku, he challenges Ibaru to another Hunter Battle. Then, Ibaru orders Enkaku to fight Shout... Will Shout win the battle and reclaim Enkaku!?

News of Captain Omegahorn's victory spreads throughout the towns, and public opinion towards the Shout and the Eval Alliance begins to change. Inspired by this, Eir declares himself to be "Captain Eir," but..

Shout and Enkaku defeat the hunters who were threatening the people in the town of Imboca. They are welcomed by the town's leader, Warren, and recruited as bodyguards.

Monsters with parts of their bodies mutated to resemble horned beasts, known as "Kakuzyu Men," attack people. Contemplating "what Captain Omegahorn really is," Shout sets out to hunt the monsters.

Captain Omegahorn, who continues to hunt down Kakuzyu Men, has become beloved by many. Suddenly, a gigantic mecha appears in the sky, causing chaos among the people. And who descends from that mecha...? A visitor from another world!?