The Empire army is fighting a losing battle at the Rhine theater before Platoon 3 mages arrive led by Second Lieutenant Tanya Degurechaff who blows up the enemies below using an explosion spell. The Empire was once a prime military power but is now surrounded by several strong enemies. The Empire implemented Plan 315, placing small military bases on the border to hold back the enemy while allowing the highly mobile main force to support each base in turn. However, the main force is delayed and reinforcements are pinned down. On the battlefield, when two mages, Harald and Kurst disobey Tanya's orders and are insubordinate, so she sends them to the rear on standby in a pillbox. Meanwhile the 403 Company artillery observers have come under attack from enemy mages. Tanya proposes a delaying action but says rescue may be difficult. When they encounter the enemy mages led by First Lieutenant Augustin Hosman, Tanya orders the three members of her platoon to rendezvous with Lieutenant Schwarzkopf and engages them herself. With a demonic gleam in her eyes, she fights them and then demands that they stand down. They refuse, so she uses a powerful spell that shoots a giant explosive bullet, wiping out the rest of the enemy mages. Later, in the Republican capital Parisee, they discuss Tanya who their troops call "The Devil of the Rhine". At the Empire's Strategy and Operations department, Lieutenant Colonel Rerugen is concerned that Tanya Degurechaff was sent to Rhine theater, he calls her a monster in the form of a girl. Meanwhile Corporal Viktoriya Serebryakov learns that Kurst and Harald are dead after an enemy bombed the pillbox, something Tanya had already anticipated.