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."

Full Metal Panic? Fumoffu depicts the adventures of Kaname and Sousuke as they try to live their normal school lives despite the chaos they inadvertently cause.

[Written by MAL Rewrite]