Horobi no Ko starts with a flash back to Riki's childhood displaying the terrible fate of his mother and how he himself was taken away from his twin brother Nachi during a game of hide-and-seek, with Nachi's plaintive cry haunting him through the years. Riki has a six-pointed star emblazoned on his hand, while Nachi has a swastika on his, the significance of which go unexplained. Riki finds himself in the town of Misaki, dotted with illegal nuclear power plants and run by a religious fanatic military organization called God's Judgment. He is taken prisoner and made to fight in gladiatorial matches in a sprawling arena. He finds his brother, whose special powers have given him the name of "Savior," but his reunion with his resentful sibling turns sour rather quickly.
