While playing with his friends on the docks of Yokohama Bay, Hoshino witnesses a strange-looking giant monster rise from the sea, the monster Gesula! It originated from Brazil, and is in search of its favorite food, cacao beans. However, Hoshino and his friends have been kidnapped by the notorious jewel smuggler Diamond Kick and his gang, who hide out in a warehouse. To complicate matters, not only is there a huge shipment of cacao beans inside the warehouse, but one of the shipments contains the diamonds that Diamond Kick and his gang were searching for, with Gesura quickly drawing near! Will the Science Patrol, and Ultraman, save the children, catch Diamond Kick and his gang, and stop Gesura?