Courage, friendship, and adventure meet when jr. high student Kiyo and Zatch Bell, a strange boy with magical powers, team up to win the ultimate battle!Zatch, Kiyo and their friends are in their most dangerous predicament yet—inside the body of a mamodo so big, it could swallow a skyscraper! The evil Riou wants to release the giant mamodo Faudo from his prison, and to stop him, they'll have to fight their way through the monster's heart, his brain, and the rest of his enormous organs! But are even Riou's normal-sized allies too much for our heroes to handle? To win this battle, they'll need to have guts—or get inside guts! For his 14th birthday, Kiyo received a strange little boy named Zatch Bell as a bizarre gift from his father. Kiyo soon discovers that there's more to Zatch than his dad ever realized—Zatch is a mamodo child with magic powers that are unleashed by reading spells from a mysterious red book...and there are 99 other kids like Zatch who must fight one another to become the king of the mamodo world!