65 million years ago, an alien race known only as the Creators came to Earth to develop bioweapons. After experimenting with and creating new life forms, they created humans and used them as the base for powerful shapeshifting creatures called Zoanoids, which are the basis for werewolf myths and other such stories. The Guyver itself existed prior to these experiments and was used by the Creators as a space suit of sorts, and through an experiment, a human being activated a dormant Guyver unit and became the very first human Guyver, dubbed Guyver Zero.