Saito is a high school student who was suddenly summoned to the parallel world of Halkeginia one day. Searching for a way to return to his home world, he lives as a familiar to the beautiful magical girl Louise. At the Tristain Academy of Magic, which she attends, summer vacation has ended, and Saito and his mistress, who worked part-time in the capital's shopping district, also returned to school. However, preparations are made to wage a full-scale war with Albion, and it is decided that most of the students will join the ranks of the active army, then Louise, taking Saito with her, returns to the family estate to receive permission to join the army. However, she was unable to obtain permission, and instead her relatives, having learned that the girl fell in love with a person of lower social status, make a fuss... What will happen tomorrow to Louise and Saito, as well as to Tristain?! There's an even newer plot twist in the wildly popular thrilling romantic comedy about a parallel world!