In the year Universal Century 0079, the Earth Federation and Principality of Zeon battled on opposite sides of the deadly One Year War. During one skirmish, infamous Zeon pilot Char Aznable successfully infiltrated an enemy base and stole a prototype mobile suit called the Gundam. With this powerful weapon, Char helped his allies achieve a decisive victory. However, in a freak accident involving the Gundam's advanced technology, Char vanishes alongside his signature red mobile suit.

Six years later, pockets of war continue to rage on. Teenager Amate "Machu" Yuzuriha lives on a quiet space colony with her mother. Though her classmates attend taxing cram schools, Machu yearns for a more exciting life. Her wishes are answered through the crash landing of the Gundam QuuuuuuX, a state-of-the-art mobile suit used by a squad of Zeon soldiers. Machu discovers a natural affinity with the suit, and she uses it to fend off Federation forces. She is aided in her efforts by the mysterious Shuuji Itou, who pilots a Gundam that bears a remarkable resemblance to the one once used by the missing Char.

Unbeknownst to Machu, her brawl is witnessed by a group of mecha enthusiasts who use mobile suits to fight in duos for competitive sport. In the pursuit of a thrilling life and human connection, Machu partners with Shuuji and engages in a series of escalating clan battles as hints of a greater conflict loom above her.