Thousands of years have passed since the war of Planet Gradius and sub-space Bacterion. The legend of the combat aircraft has become a myth... In 21st century Earth, the mysterious Bacterion visits Earth and continues the war. The St. Gradius high school 2nd grade student Aoba Anoa was sought by the secret anti-Bacterion organization "G" for her talents, and became the maiden 'Angel'. She was given a Riding Viper named Vic Viper. Millennia from the legend, new myth has begun.