In the Twelve-World, the mysterious land in an unknown dimension, the humans, monsters and spirits coexist in harmony for a long time. All the lives are protected by the Princess of the Needle Tower in the Zero World. All of a sudden, the balance of the Twelve World is crumbled. The Princess of the Needle Tower is confined to sleep. After losing the protection of the Princess, the monsters are released from the chain of life and become uncontrollable. They begin to attack the humans...

The troubleshooters called the Great Children dealing with the incidents involving the monsters are the only ones who can restore the harmony and balance of the Twelve World. Spaak is the best of the group of the Great Children and the center of children's admiration. He learns that the Zero World was invaded. On the way to the Needle Tower, he meets an incredible boy, Bucky. Young and ambitious Bucky wants to be the strongest man and conquer the world. Spaak feels something special in Bucky and chooses the boy to be his successor. So, Bucky sets out for his quest to be the best Great child of the world. While going ahead recklessly, Bucky learns that the monsters are controlled by an unknown power from another dimension. He meets Kai, Pinky and other fellow Great Children and continues to travel to the Needle Tower with them.<br><br>
(Source: Enoki Films)