A young girl named Nono has left her home behind, to come alone to the big city to pursue her grand dream of becoming a space pilot. But reality is harsh, and she spends every day instead at the diner near the spaceport where she lives and works. Then one day, while being harassed by one of the regular customers, a real-life space pilot named Lal'C comes to her aid. Lal’C is a member of “Topless”, a team of elite, psychic pilots who operate Buster Machines whose mission is to protect people of the Solar System from space monsters. During a monster attack, Lal’C witnesses Nono’s superstrength which helps her defeat the alien.

The elite Topless make their rendezvouz, as the order is given to launch a major operation to stop the horde of Space Monsters known as Jupiter Express. Tycho, who lost her Buster Machine in her last battle, sees a rival in Nono for the pilot seat of the newly constructed Quatre-Vingt-Dix. Then the two of them meet some children who say they have "a favor to ask a Topless"...

The real enemy, the Fluctuating Gravity Well, closes in on mankind!! What will be the fate of the Sol System?! Finally, Nono's true self has been revealed. Since the shocking Titan Incident, the Topless have been placed under house arrest in the remotest part of the Sol System, their abilities sealed up. With their very existence denied, Lal'C and the other pilots are now at the mercy of fate. But another catastrophe is closing in on the Sol System, as the corps of Space Monsters gather around their nest. The real enemy of mankind, the fluctuating gravity well, has at last appeared. The time has come to launch the strongest fleet in the Space Force--and the Buster Machine # 7!