The producers of Machine Girl and Tokyo Gore Police team with the special effects wizard behind Uzumaki and Gamera 3 to deliver a spirited kaiju romp about a mischievous yokai that threatens to decimate Tokyo. Kanako left for Tokyo with dreams of success. When those dreams fail to materialize, she returns to her village in shame and moves in with her elderly grandmother, the caretaker for the local river spirit. Before long, Kanako has taken over her grandmother's responsibilities, dutifully feeding the kappa a steady diet of cucumbers and regularly cleaning its shrine. Trouble starts to brew, however, when a team of World War II scientists attempt to transform the kappa into a weapon of war, and instead unleash a devastating force of destruction on the unsuspecting citizens of Japan.