Sergeant Sousuke Sagara returns to Jindai High School to protect the precious war asset, Kaname Chidori, from any threat. However, his lack of social skills and real-life experience result in comical yet dangerous situations, endangering the peaceful school life Kaname longs for. As Sousuke continues to bring a wide range of weapons to school as a means to solve threats—real or fake—Kaname struggles to fulfill her duty as the student council vice president all while keeping him in check.

To ensure a successful mission, Sousuke is occasionally forced to use the costume of a famous amusement park mascot called Bonta-kun. With his technical expertise, he eventually transforms the exuberant uniform into a cutting-edge exoskeleton that has only one dysfunction: the voice translator can only produce the sound "mofu."