The Republic of San Magnolia: in the shadow of the peaceful lives of its citizens, countless lives are being decimated. Juggernauts are unmanned combat machines manufactured by the Republic in order to fend off the Legion, an army of drones deployed by the neighboring rival—the Giadian Empire. However, the unmanned nature of the Juggernaut was nothing but a fabrication. The Juggernaut are piloted by a group of young boys and girls known as the "Eighty-Six", who continue to fight day and night to restore their rights that were stripped by the Republic. A Republic Major—Lena—who is determined to help liberate the Eighty-Six is put in charge of the elite Spearhead Squadron. However, she comes across a suspicious rumor that the leader of the Squadron—Undertaker—has a tendency to destroy the psyche of the command officer in charge.
The Republic of San Magnolia has been at war with the Giadian Empire for years. However, thanks to both sides using unmanned drones to fight, the Republic boasts that they are fighting an ethical war since no humans are actually being killed. However, in reality, the Republic's Juggernauts are actually secretly being piloted by humans called the Eighty-Six, from the Republic's unofficial Eighty-Sixth Sector. Major Vladilena "Lena" Milizé is a Handler, an officer in charge of commanding Eighty-Six in battle, though she has a reputation for treating the Eighty-Six as humans. One day, Lena is suddenly appointed to be the Handler for the prestigious Spearhead squadron, made up of the most elite Eighty-Six Processors. However, the unit's leader, Shinei "Shin" Nouzen, known as the Undertaker, has a reputation for destroying Handlers, as every Handler that has attempted to command him has either requested transfer, retired or even committed suicide. Meanwhile, on the frontlines, the pilots of Spearhead live life as best they can, while taking personal glee at tormenting every Handler sent to them. However, during one battle, one of them is mortally wounded, and Shin lives up to his name by mercy killing him. Later that night, Lena contacts Spearhead and introduces herself to them.
Differences from Light Novel
- Contrary to the anime opening up with the sounds of Undertaker breaking the psyche of a Handler, in the novel's Prologue Undertaker does not harm the Handler. The Handler, instead, hands over command of the battlefield to undertaker before the Spearhead Squadron's interception with the legion and escapes the battle by cutting transmission. Furthermore, while in the anime the Handler curses the Eighty-Six to destruction, the Handler in the novel shows an apologetic behavior.
- Though in the novel, the timeline is presented using both Republic Year and Stellar Year calendars, the anime exclusively uses the Stellar Year calendar only.
- Margareta Milizè, Lena's mother, is introduced during breakfast early in the episode. In the novel, she is introduced later in the next morning after the battle with Pleiades' Squadron.
- During the battle involving the Pleiades' Squadron, the squadron leader Pleiades and 6 other units died in battle, along with 5 other units destroyed in prior battles leaving only 13 of 24 units units left alive at the time Lena's designation was changed.in the novel, Pleiades survived the battle and only 7 units were destroyed during all interceptions, leaving with 17 units alive.
- Lena met Karstahl and was appointed as Spearhead Squadron's control officer before the battle with Pleiades' Squadron . In the novel, she meets Karlstahl and takes up the position in the Spearhead Squadron a day after the battle with Pleiades' Squadron.
- The introduction of the Spearhead Squadron which also recounts the death of Kujo is based loosely around the Triage - Black Tag novella collection. In the original novel, the introduction is set ten days after the death of Kujo.
- Though in the anime Shin shoots Kujo with a handgun to ease his death, it the novel he died by getting caught in an explosion of self-propelling mines, a trap set by the Legion.