Poverty runs rampant on the surface of Mars and jobs are scarce due to the stranglehold Gjallarhorn, a military faction established by Earth, has on the economy. In an effort to grant her Martian city its independence, Princess Kudelia Aina Bernstein requests that she be escorted to Earth by Chryse Guard Security (CGS)'s Third Group. However, CGS comes under attack by Gjallarhorn in an attempt to prevent Mars's movement towards independence, and Kudelia and her group are abandoned. The Third Group, comprised of child soldiers led by Orga Itsuka, starts a rebellion against the adults who had left them behind.