Despite decades passing since humanity's war with the Space Monsters began, no one remains who knows how it all started, and even records from that time are rare. Despite this, humanity continues battling against the monsters, relying on the "Topless": a small group of exceptional pilots with unique abilities that allow them to operate the Buster Machines, the only weapon capable of defeating the Space Monsters. Nono, a girl from a small Martian town, has always heard stories of the legendary pilot "Nono-Riri" and dreams of leaving her simple life behind to follow in her idol's footsteps. Though she knows little of the dangers that await her, she is determined to make it happen. After a stroke of luck, she crosses paths with lone Topless pilot Lal'C Melk Mark and decides to bet everything on following her, whatever the cost may be.