Gaira, a humanoid sea beast spawned from the discarded cells of Frankenstein’s monster, attacks the shores of Tokyo. While the Japanese military prepares to take action, Gaira’s Gargantua brother, Sanda, descends from the mountains to defend his kin. A battle between good and evil ensues, leaving brothers divided and a city in ruins.

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?