Brilliant surgeon Ukyo Retsu performs an operation to remove a cancer from a mysterious old woman. The "cancer" turns out to be a 5000 year-old demon, a dark messenger from Japan's ancient past heralding a demonic invasion of the Earth. Ukyo travels to the remains of an ancient city where he finds a gateway in the fabric of time which enables him to travel back 5000 years. There, in Earth's past, he discovers a Race of Demons who are planning to use the gateway to travel to the present in order to destroy mankind and make the Earth their own. Can Ukyo defeat the ancient Race of Demons and save the Earth, or will mankind be wiped out?