During the Summer holidays, Gash and gang decide to head for Fuji Mountain for a picnic gathering. There, they encounter a girl with a white magical book. Her name is Kotoha and her book has a message saying that Gash's mother is located a cave in the forest. However, when they eventually found the cave, there was already a blond-haired youth by the name of Wiseman. In order to rescue Wiseman, Gash and the others attempt to proceed into the depths of the cave and stumble upon the entrance to another world. Soon later, the strongest warrior, the Black Knight, appeared before them. Thinking that Gash was the one who stole the 101th magical book, the Black Knight started to attack them. Gash and Kiyomaro have to find the real criminal in exactly 24 hours, or else they will be stuck in the alternative world forever.
Zatch and Kiyo go on a camping trip in the forest near Mt. Fuji with their friends. When they meet a girl name Ctoha, who found a special book that tells her of things to come, her mother suddenly gets seriously sick. Now, to find a cure (and Zatch's mother), they must go to a cave in the forest. In the cave, Zatch and Kiyo are taken to the mamodo world, while Ctoha takes a strange man named Wiseman to cure her mother. In the mamodo world, Zatch and Kiyo are chased by the Magister Black Knight, who thinks that Zatch has stolen the 101st book, which was to be for the King. Now, Zatch has to clear his name and return to the human world within 24 hours so that he can defeat Wiseman, who is actually a mamodo that stole the 101st book, and save Ctoha from him.