Ten years after the destructive Great War, the nations of the world decided to turn to espionage rather than open warfare to resolve their conflicts. In the Din Republic, master spy Klaus is given an "Impossible Mission" which if he manages to pull off, will cement his reputation as the "Greatest Spy in the World". As part of this mission, Klaus gathers seven young spy cadets who are struggling in training, including a girl named Lily, into a team codenamed Lamplight. He explains that he will help train them to prepare for an Impossible Mission in the Galgad Empire, but while he proves to be a master spy, he is actually a poor teacher. Thinking that Klaus intends to use them as sacrificial pawns, Lily ambushes Klaus with poison gas in an attempt to force him to disband Lamplight. However, Klaus reveals he already saw through Lily's ambush, but he is impressed how she took the initiative to try and improve her situation, which gives him inspiration on how to teach the other students. The next day, Klaus installs Lily as the team leader for Lamplight and assures them that he won't let any of them die. In order for them to learn the skills they need, Klaus challenges the students to defeat him in a game of espionage.