This installment, which occurs sometime after Thunder Force IV, takes us away from the conflict between the Galaxy Federation and the ORN Empire, this time taking place on Earth in the future. In the previous installment, Rynex was badly damaged after destroying its final target, forcing the pilot to eject. The damaged fighter drifted into the Sol System, and it was captured and studied by scientists. In the South Pacific Ocean, a large, unmanned artificial island named Babel was created, and then the supercomputer known as the Guardian was constructed. However, as research in Vasteel technology had advanced, Guardian suddenly achieved full consciousness and declared war on humanity. As a result, Cenes Crawford and her team of hotshot pilots have been sent to destroy the Guardian and its forces in order to save humanity.
—Anonymous