The protagonist is a student sent to “The School” midway through the war, only to encounter the impending “School War” upon enrollment. To eliminate weaker students, the school periodically stages these “School Wars,” setting a maximum survivor count to force students into mutual slaughter. The school claims students who submit valuable inventions will be granted freedom outside its walls, while those failing to make independent research progress for too long will be purged. To survive or escape, students formed various factions. Backstage Machina was one such group. Its founder, Polar Night, initially focused on developing AI language model robots for entertainment and companionship. However, after the school discovered her mechanical talents, she was assigned by higher-ups to shift her research toward military machinery. Following a summons, she left the campus and remains missing to this day. The protagonist accidentally stumbles into Backstage Machina during its low period, encountering Polar Night’s apprentice and assistant, Bella and Belilo. Due to a shortage of manpower, Bella takes the protagonist in. After helping repair some circuits, the protagonist accidentally enters Polar Night and Polar Day’s office, where they uncover the story of Polar Night and Polar Day through puzzle-solving.