Sergeant Sousuke Sagara returns to Jindai High School to defend the valuable war asset, Kaname Chidori, from harm. However, his lack of social skills and real-world experience leads to funny yet perilous situations, jeopardizing Kaname's serene school life. As Sousuke continues to bring a variety of weapons to school to deal with dangers, real or imagined, Kaname tries to complete her duties as student council vice president while keeping him in control. To assure the mission's success, Sousuke is periodically compelled to dress up as Bonta-kun, a popular amusement park mascot. He finally converts the flamboyant outfit into a cutting-edge exoskeleton with only one flaw: the speech translator can only make a single sound.