It was the dawning of a new century, as an age old prophecy concerning the decimation of humankind was inching toward reality. As overpopulation continued to run unchecked across the globe, the world's food shortage become a dire issue to the Earth's governing bodies. Desperate for a quick fix, the Japanese nation turned toward using Gibberellin, a plant hormone capable of tripling the rate of growth on a normal harvest. Yet, the nation's problems would not be solved so easily, as pollution continued to rage across the country. Despite the fact that the Japanese government had imposed restrictions to protect the environment, corporations merely developed techniques to mask their own output, as toxic emissions continued to be poured into the sky while being invisible to the naked eye. The situation reached critical levels in portions of Japan, as children were forced to wear surgical masks to school while entire flocks of birds fall dead out of the sky. However, mother nature finds a way, as the excessive amounts of pollution and the Gibberellin hormone caused normal species to mutate across the country as they adapted to their changed surroundings. One such mutation was the Giant Slugs, who were merely an enlarged form of their smaller brethren. In spite of their seeming in-hostility, the Japanese government wasted no time in dispatching the Self Defense Force to the reported area to exterminate the creatures. Equipped with flamethrowers, the soldiers quickly laid siege to the slugs amidst an ever growing crowd of onlookers. As doctor Ryougen Nishiyama rushed forward to try and collect one of the slugs for a sample, he was held back sipposedly for his own protection. However, the government's true intention was to cover up the source of the creature's abnormalities which was made all too clear to the doctor, as the last of the creatures were burned alive.