A decade has passed since the devastating Great War showcased the lethal potential of weapons. In a bid to prevent another catastrophe, governments around the world have turned to espionage to further their agendas.
In the Din Republic, a spirited young girl named Lily harbors a deep desire to become a spy and serve her nation. However, her confidence wavers as she struggles academically. Just when doubt begins to cloud her aspirations, Lily's passion is reignited when she receives a provisional graduation offer to join the Lamplight spy team—an opportunity she eagerly embraces despite its enigmatic nature.
Upon reaching her destination, Lily is taken aback to find six other girls awaiting her arrival, each having faced their own academic challenges. Their meeting takes an intriguing turn when a mysterious man named Klaus emerges, unveiling an "Impossible Mission": infiltrate the Galgad Empire with just a month of training. Though skeptical at first, the girls eventually agree to join forces under Klaus' guidance, recognizing that this may be their sole chance to prove their mettle as spies.