On Earth, it is now the year 2032. Kazumi and Noriko are given a late graduation from Okinawa Girl’s Space Pilot High School after they return from space. Noriko thinks about how she was only gone for four months, but ten years had passed on Earth. Reiko is now an instructor at the school. After the ceremony, Noriko wonders if she should feel privileged to graduate at seventeen, but Kazumi reminds her that she’s twenty-seven according to her birth certificate. Noriko passes a mother and child, and recognizes the mother as Kimiko. Kimiko, who is now Kimiko Akai, brings Noriko up to speed on their friends while her daughter Takami plays in a sand box. Noriko sees something in orbit and Kimiko tells her it’s the battleship Eltreum. She says it’s an Earth evacuation ship. Kimiko asks Noriko if she can use her connections to make sure Takami can get a spot on the Eltreum. Later that night, Noriko tries to call Kimiko, but she’s gone out. She tells Takami to apologies for her. Noriko wonders if her father also felt like he had been left behind when he returned from space. A large mass of enemies that blot out space is detected outside the Sol System. In her room, Noriko is informed that Ohta wants to see her. Kazumi argues with Ohta, which ends with Ohta slapping Kazumi. Noriko sees this and Kazumi walks out with tears in her eyes. Ohta coughs up blood and collapses. Noriko tries to call and ambulance, but Ohta stops her. He says not to tell Kazumi about it or he’ll kill her. The next day, Noriko and Jung relax on the beach. Jung says she’s decided to give up on Ohta and that they’ve only got one life to live. Later, in the bath, Noriko thinks back to her conversation with Ohta. He told her about the incoming enemy fleet and that Gunbuster is their only hope. He said that together with Noriko and Kazumi, Gunbuster is invincible. He apologized for not being able to protect Noriko’s father and asked Noriko to keep his illness a secret from Kazumi because she wouldn’t be able to fight if she knew. He asked Noriko to protect her. Noriko wonders if she can protect Kazumi and realizes that she already knows about Ohta’s illness.
In the Imperial city of Tokyo, the military brass tries to plan their next move. The Eltreum isn’t ready and they don’t know what else to do. Ohta barges in and says he has a plan. He proposes sending in the decommissioned Exelion and self destruct it, making an artificial black hole to suck in the Space Monsters and the planetoid Jupiter 2. He says the Buster Machines will escort it and that it’s the only option available to them. Noriko and Kazumi head to Tokyo for the mission. Noriko tries to make small talk, but it doesn’t go so well. Kazumi says six months will pass on Earth while they’re gone. Noriko asks about Ohta’s condition, but Kazumi says they have the lives of billions to worry about. Noriko is glad to see Kazumi acting like her old self. As Buster Machines #1 and #2 prepare to launch, Ohta arrives to see them off. Noriko tells Kazumi and asks if Kazumi will marry him when she gets back. Noriko says they make a great couple and that Ohta will need some one to take care of him. Kazumi tells Noriko that Ohta has space radiation syndrome. He might not live six more months. The Buster Machines take off and rendezvous with the unmanned Exelion. They head into the enemy fleet. The Buster Machines start clearing a path to the center of the Space Monster fleet and Noriko sees that four months have already passed on Earth. Kazumi can’t take it anymore and she goes into reverse. The Exelion gets impaled with two Space Monster boarding vessels. Kazumi cries that even if they make it back to Earth, Ohta will be dead and she never got a chance to say she loves him. That time they were arguing, she was hoping he would kiss her and say he loved her. She says she can’t stand that she’ll never see him again. Noriko tells her to pull herself together, saying that Ohta probably wanted to be with her, but had to forsake himself so Gunbuster could succeed. They have to make the most of his last six months and fight. Kazumi understands and decides to fight so she can live in the same time as Ohta. They combine their Buster Machines into Gunbuster. Noriko uses the Super Lightning Kick to break through the Space Monsters and land on the Exelion. Noriko sweeps the area with the Buster Beam. A group of 3,000 come from below, but Noriko destroys them all with her Homing Laser. She uses Buster Missiles to destroy a cruiser-class and leads the others away from the Exelion. A mass of lasers head towards them, but Noriko blocks them all with the Buster Shield. She then blows them all away with Buster Beams. Two mother ship class Space Monsters try to crush them, but they are destroyed by the Double Buster Collider. The Exelion makes it to the center of the Space Monster fleet, where it becomes a black hole and sucks them all in. News of the mission’s success reaches Tokyo, where they say that the shockwave will hit them in six months. Gunbuster lands outside a hospital, where they find Ohta still alive. Kazumi jumps into his arms and says she loves him. Noriko leaves them alone and apologizes to Smith because she said she wouldn’t cry anymore. She asks her father if Kimiko would be proud of her.
Noriko and Kazumi return to Earth to find that ten years have passed. Like I said before, time dilation sucks. Since Noriko’s major developments are done, focus this time is put on Kazumi. Before she was just portrayed as the elegant (and slightly bitchy) ‘big sister’ and nothing more. Here we get to see her vulnerable side and her feelings for Ohta. Not being able to be with her loved one before he died took away her will to fight, but thanks to Noriko, she’s able to overcome it. This leads into one of the greatest battles ever, as Gunbuster rakes up a kill count that has yet to be surpassed. Just some good old fashioned super robot hotblooded asskickery. Though the Exelion’s explosion will have unforeseen repercussions in the future. Ohta manages to survive (because he’s just that awesome) and Kazumi is able to tell him her feelings. Now all that’s left is the epic finale.