A Geological Survey Ship arrives on Saturn’s moon, Titan. They head to an excavation site and three scientists discuss what’s buried there. One suggests that it’s an alien Buster Machine from Sirius. The ship runs into the Serpentine Twins’ Buster Machine, Quarante-Deux. Nicola, who is on the survey ship, says they have to leave the airspace. They arrive at a base and the crew unloads equipment. They see Nhan, Roy, Pasika, Gurka, Tycho and Lal’C enjoying themselves at a pool. Nicola tells the crew not to wander around and goes to join the other Topless. Later, while changing, they discuss the Fluctuating Gravity Well and how it could be a single digit Buster Machine. They wonder if Nono will be the pilot, and comment how Lal’C’s score has increased because of Nono’s help. Lal’C said that’s not true, but runs into Nono when she opens the door. The other Topless tease Nono, saying she should just go back to the country and get married. Nono scrubs the pool and wonders if she could get Lal’C to acknowledge her if she had a Buster Machine too. Tycho just listens silently. The Serpentine Twins eat a feast of meat, and Nicola is disgusted by the smell when he enters the room. Nono watches the Buster Machines and thinks that if she had one, she’d become a Nono-Riri. Nono heads down into the excavation site. The Serpentine Twins explain that the terrain is made from the bodies of dead Space Monsters that tried to bury the Fluctuating Gravity Well. Despite that, it’s still alive and is becoming more active. They add that if they can control it, they’ll have nothing to fear. Nicola says he doesn’t have much time remaining. The Twins tell him not to worry since he knows their true age and the secret behind it. They offer him a piece of meat. Nono reaches the bottom, but she gets a weird feeling. The alarms then go off. She is sent before the twins, but they tell her not to worry about it. They tell her about Buster Machine Trente-Trois, which had gone missing but was discovered on Pluto. They say Nono should make it her own. Tycho tells Lal’C that Nono is going to Pluto and suggests that it’s Lal’C fault. Tycho also notes that the Buster Machines have been acting weird since they arrived. Lal’C says that’s not possible since she knows everything about Dix-Neuf. Tycho says a Buster Machine might open up to some one like Nono, and Lal’C notes that she sounds like Casio. At some remote outpost, Casio laments that he got sent out there because he guessed that the Serpentine Twins were lying about their age. He adds that it’s fine since he got to learn about Trente-Trois. Nono prepares to board her ship, but Lal’C tells her she should just stay. The ship takes off and Nono says she feels very far away from Lal’C, but she’s going to close the gap.
Lal’C thinks back to how she used to show Nono pictures from Earth. Lal’C figures that if Nono-Riri was a Buster Machine pilot, she must have been a Topless. In that case, Nono could never become one. Lal’C meets Tycho in the laundry room, and Tycho tells her she gave Casio a heads up about Nono. Nono arrives at the spaceport on Charon. All the Buster Machines are positioned around the excavation site as the Serpentine Twins use Quarante-Duex to operate on the Fluctuating Gravity Well. At the same time, a massive number of Space Monsters come out of the Red Milky Way. The Charon spaceport shuts down, but Casio arrives to pick Nono up. The Space Monsters arrive at Titan, and the Buster Machines intercept. Half of the Space Monsters break off and head towards Pluto. Nono and Casio head towards Pluto, but are attacked by the Space Monsters. The Serpentine Twins note that the Space Monsters went after Nono as planned. The Fluctuating Gravity Well awakens. The Buster Machines continuing fighting but are overwhelmed by the numbers. The Twins tell them they’ve done well and the Fluctuating Gravity Well beings to surface. Casio and Nono approach Trente-Trois, but their shuttle crashes. The Fluctuating Gravity appears, and the Space Monsters attack it. The Gravity Well fires a blast that wipes out most of the Space Monsters. The Twins reveal that it is not a Buster Machine, but an ancient Topless. Nicola almost vomits, realizing where the meat he ate came from. Casio and Nono continue on foot, Casio telling Nono that piloting a Buster Machine is a frightening thing and that she doesn’t need it. He adds that Lal’C doesn’t think so either, and Nono recalls how Lal’C invited Nono to her house on Earth. Casio says that all Topless have are the Buster Machines, and that once they loose them, they can’t find a reason to live. He says Nono-Riri was probably the same. Nono says he’s wrong. Casio says he’s still a Topless so he’ll use Trente-Trois, but once they arrive there, they see that Trente-Trois is just a skeleton. The Space Monsters gather on the opposite side of Titan. The Fluctuating Gravity Well turns on the Twins, firing a blast that kills them and travels through the moon, destroying the Space Monsters on the other side. Nhan is killed by rubble and the Gravity Well continues firing. Gurka and Pasika are also killed. Lal’C asks Dix-Neuf what the Gravity Well is and she realizes that it is a true Space Monster. She wonders what they’ve been fighting against up until now. Back on Pluto, Nono is surrounded by Space Monsters and some how hears Lal’C getting hurt. Nono’s hair glows red and she creates a singularity in her hands. She grabs it and she and the Space Monsters disappear. On Titan, the Fluctuating Gravity Well prepares to finish Lal’C and Tycho off, but Nono warps out in front of them, absorbing the Gravity Well’s blast. Nono introduces herself as Buster Machine #7. A group of Space Monsters, actually known as the Buster Corps, warps out behind her and attacks the Gravity Well. Nono says that she was an idiot because she did’t realize a true Nono-Riri has a Buster Machine in her heart. The Fluctuating Gravity Well charges at Nono, but she uses her Buster Beam Slash to cut it, and Titan, in half. The Buster Corps help everyone escape from Saturn. Nono lands in Dix-Neuf’s hand.
Now this is more like it! Like Gunbuster episode 4, this is where things really pick up. Nono wants her own Buster Machine, so she goes off to Pluto to get it. Lal’C might try to act otherwise, but we see that she really does like Nono and wants her around. Meanwhile, everyone is preoccupied with reviving the Fluctuating Gravity Well, which turns out to be an authentic cruiser-class Space Monster. Bet no one saw that coming! Some of the Topless get killed off, but Nono realizes her true power and awakens as Buster Machine #7 in time to save Lal’C. Nono’s epic entrance and her cutting Titan in half is certainly on par with the original OVA. You can’t help but sing along once that Buster Machine March kicks in.