Full Metal Panic!

Full Metal Panic! summary:

Jindai High School was a relatively safe place, right up until Sousuke Sagaka transferred there. A total nut, he wreaks havoc on the school’s student body and gets into a world of trouble with the teachers!
But there’s more to Sousuke than meets the eye–not just a h.e.l.l-raising student, he’s actually a member of an elite military unit, on an undercover mission to protect the beautiful schoolgirl Kaname Chidori from the KGB. Discover the mystery as this comedy-action-science-fiction story unfolds!