The Academy's Weapon Replicator

Etius is a game that no one has ever managed to clear. The moment all possible strategies fail and a game over screen appears, the player awakens inside the world of the game as the extra character, Frondier. His sole ability is "Weaving," a skill that merely saves and replicates objects as virtual illusions. Immediately after his arrival, a main quest appears, warning him of humanity's impending destruction and charging him with changing its fate. Armed only with the capability to create virtual duplicates, he must copy everything he can to overcome the odds and forge a new destiny.