Seven years prior to the series, a meteorite struck the Shibuya district in Tokyo. An alien lifeform, known as the Worms, emerged from the meteorite and became a threat to humanity. Souji Tendou has trained seven years while waiting for the Kabuto Zecter so that he may properly take up the name of Kamen Rider Kabuto. Making many enemies while at the same time meeting other Riders with mysterious origins, Tendou attempts to accomplish his goal at all costs: destroying all Worms that otherwise threaten humanity. He meets Arata Kagami, who later becomes Kamen Rider Gatack, the two work together to save humanity from the alien Worms before the hidden conspiracies within the ZECT organization and the Natives species come to light.