Female teacher Keiko Sawaguchi was once abducted by the terrifying scientist Professor Zark, a man as evil as a demon, and forcibly underwent surgery to fuse with snake DNA, transforming her into Cobra, a superpowered female ninja. Before this transformation was complete, she resolved to escape Zark's base, and ever since has continued her battle in the shadows to stop his sinister schemes. However, one day, she is defeated by Skull Tarantula, a mysterious monster created by Zark. Professor Zark's horrifying scientific experiment now targets her once again—this time, extracting the bio-snake parasitizing inside her body through her rectum, an extremely cruel method. Screaming, "Ah! It's tearing, it's ripping apart!" the female ninja grimaces in agony, her spirit broken. Impaled by Skull Tarantula's tentacles, her fate hangs in the balance—.