The year is C.E. 73 and the conflict between Naturals and Coordinators remains unresolved, resulting in a renewed war between the Earth Alliance and PLANT. Sven Cal Bayan, a Natural pilot with the highly regarded EA unit, the Phantom Pain, dutifully carries out his team's missions to suppress Coordinators. Meanwhile, Selene McGriff, a Coordinator researcher at the neutral DSSD organization, designs the GSX-401FW Stargazer mobile suit for space exploration. Despite their contrasting pasts, fate brings them together as the escalating war takes its toll.