Full Metal Panic!

Sousuke Sagara knows combat far better than ordinary school life. As a soldier of Mithril, he is assigned to protect Kaname Chidori, a student whose hidden knowledge makes her valuable to people pursuing advanced military technology.

Posing as her classmate is a constant disaster: Sousuke treats harmless situations as threats and leaves Kaname to deal with the consequences. When real enemies close in, however, his battlefield skills become essential, and the secret behind her importance can no longer remain distant from her daily life.