Full Metal Panic Overload 5! Shou ji Gatou. 2003.

Jindai High is under lockdown, and it's no mystery who the culprit is. But once Sosuke starts filing the classrooms with gun toting teddy bears everyone stars to wonder if he's finally fipped out. Theres more to these teddies then meets the eye, though, and theres more to Sosuke than he’s letting on -his mission to protect Chidori is over and he’s been ordered back to base! And just to make sure he complies, a familiar face shows up with a teddy-bear army of his own, leading to a battle that could bring the school down!

THE MAYHEM CONCLUDES IN THIS EXPLOSIVE FINAL VOLUME!