The Man From the South

The Man From the South (南から来た男, Minami Kara Kita Otoko) is the first story of the first episode of the anime series, Full Metal Panic? Fumoffu.

Summary
A secret admirer leaves a love letter in Sousuke's shoe locker. Instead of finding the letter, he deduces that his locker was tampered with and promptly blows it up. From its fragments, Sousuke misinterprets the letter as a death threat and confronts his "stalker".