Noriko Takaya has spent barely had a month at a training school for giant robots. The school announces they are going to select two candidates to go to the Exelion spaceship for the real missions to fight against an invading mech army. One of the choices is obviously the beautiful and leading senior Kazumi Amano, but somehow Noriko is selected for the second spot! The other girls get jealous that Noriko got the spot, suspecting it's because she was the daughter of the Admiral in a previous mission. School rival Reiko Kashihara feels that's totally wrong, and challenges Noriko to a duel.

The fleet advisor tells Captain that the aliens are going to attack Earth. Coach has been training Noriko, but Jung wants to test Noriko by challenging her to a duel. Noriko is still shaken from the death of her comrade and breaks down when they are outside. As the fleet is preparing to jump back to Earth, hoping to hide their trail in subspace, they are suddenly attacked by the aliens and everyone scrambles for their mechs. Noriko is benched for the battle. Things look bleak as most of the defense forces are wiped out, but Noriko manages to get out of her rut and moves to pilot the force's super prototype mech called Gunbuster.