In 2079, the world's first orbital elevator was built in the Pacific Ocean to commemorate the peace that mankind regained after the 3rd World War. However, during the completion ceremony, a huge red humanoid object appears from outer space. It was so powerful that mankind was defeated in vain resistance. The orbital elevator was occupied, and since then mankind has entered a war with the red hostile flying object "Vacant" flying from there.  Summer 2099. "It's been 20 years since the war started." Humanity developed the humanoid 7th generation fighter "Seventh" and succeeded in suppressing "Vacant" to the vicinity of the orbital elevator.