The Smart Brain Corporation, the world's most powerful corporation is trying to take over the world using Orphnoch, the next stage of humanity's evolution, to covertly wipe out the human population. In pursuit of this, they develop three suits of power armor, called Rider Gear (Delta, Phi, & Chi), to find the Orphnoch King, who can fix a defeat within Orphnoch DNA which causes their genetic structure to break down, often leading to death. The Rider gears are stolen by Luther, the goat Orphnoch & former cheif of Smart Brain. He sends them to his foster children (dubbed the Meteorites, after the school they attended) so they can stop the Orphnoch from acheving their goal. However, Rider gears were designed to be worn by Orphnochs, and human are unable to activate the systems without undergoing genetic modification. A young loner, Nathan Yap, is unwittingly drawn into the conflict between the Orphnoch & humans becomes Kamen Rider Phi to save the life of Maria Jardine, The Smart Brain begins targeting him in an attempt to retrieve the Phi Gear.
