In After Colony 196, a year after the Siege of Libra, the first president was elected due to the establishment of a unified government in the Earth Sphere, and weapons disappeared from the Earth Sphere, so no more conflicts occurred. However, 'Preventor', the only armed force agency that directly investigates and prevents signs of conflict, discovers traces of the manufacture of neo-titanium alloy, the material of the mobile suit, along with the code of '13th constellation'. Meanwhile, Lirina Peacecraft, who visited Colony X18999 as an ambassador, is kidnapped by a force who calls themselves 'Marimeier Army'...