When a rare species of butterfly is found in a mysterious valley in Japan, a pair of entomologists go to investigate and find more. They discover Varan, a giant monster, who decides to leave the valley and head straight for Tokyo.
A librarian is subject to a scientific experiment which goes wrong and transforms him into 'The Human Vapour'. He uses his new ability to rob banks to fund the career of his girlfriend, a beautiful dancer. The Human Vapour is ruthless in his quest for money and kills anyone who stands in his way, especially police. He soon becomes Tokyo's most wanted criminal. Can he be stopped before he kills again?
Lt. Koji Kitami is a navigator-bombardier in Japan's Naval Air Force. He participates in the Japanese raid on the U.S. Naval Base at Pearl Harbor in 1941 and is welcomed with pride in his hometown on his return. As Japan racks up victory after victory in the Pacific War, Kitami is caught up in the emotion of the time and fights courageously for the standard of Japanese honor. But his assuredness of his government's righteousness is shaken after the Japanese navy is defeated in the debacle of Midway.
