In this world, there is a world of humans and also another separate world. The world of Beasts.
Shibuya in the human world and Jutengai in the Beast world.
A lonely boy and a loner Beast that live in these two unconnected worlds…
One day, a boy encounters a Beast, Kumatetsu, and decides to go live in the world of Beasts in order to get strong. He becomes Kumatetsu’s apprentice, who gives him a new name, Kyuta. At first, they clash about everything, but their extraordinary life and training together help both of them mature, and gradually a bond develops between them just like a real father and son.
One day, when Kyuta has grown up to be a robust young man, he accidentally wanders back to Shibuya from Jutengai and meets schoolgirl Kaede. His encounter with Kaede, who teaches him about a new world and its values, makes him start wondering in which world he really belongs. Then something significant happens that involves both the world of humans and the world of Beasts. What can I do to save everyone? Kumatetsu, Kyuta, and Kaede. The time comes for each of them to make a decision.