Situated on Blue Island, the Manifestation Engine has been the answer to the world's energy problem for five years. On the neighboring island of Izu Ooshima reside the cheerful Akane Isshiki, her dependable little sister Momo, and her grandfather Kenjirou, one of the inventors of the Manifestation Engine. As they live peacefully alongside the powerful creation, it all seems like a dream until mysterious entities known as the "Alone" appear seeking to destroy it. With military forces failing to repel the invaders, Kenjirou grants Akane a special key containing the "Vivid System"—empowering her to fight the Alone. Joined by Aoi Futaba, Wakaba Saegusa, and Himawari Shinomiya, Akane and her friends stand together in the battle against the unforeseen enemy as the last hope for humanity.