Fridge Brilliance: It at first seems baffling that Sousuke's teachers wouldn't suspect his guns were real, until you realize that Japan has very strict weapon control laws. Seeing even just a handgun in real life is unthinkable for a Japanese civilian, to say nothing of the military-grade assault rifles that Sousuke was packing.
Sousuke's inability to realize the fuss about the Sacred First Kiss might appear strange until one realize that he grew up in Afghanistan, where kissing (between men) is simply a form of greeting with no romantic implications whatsoever. In episode 8, he even revealed that he had kissed men before during his time in the Middle East and Central Asia.
Fridge Horror: Pretty much all of Sousuke's Fish out of Water actions. Blowing up a locker that has been tampered with seems silly...until you realize that where he's from, that usually means there's a bomb inside.