@Sniperking It's tribal cover for... male parts. They wear this and nothing else, basically (though this big it's likely for stuff like ceremonies, since otherwise it would be impractical).
@swilson In traditional yonkoma format (look up kishoutenketsu), the punchline, or climax, is in 3rd panel. The fourth panel is for reaction, "aftermath" - which is even more fitting with the black panel, in my opinion; there's simply no better or appropriate reaction to such a big reveal.
The truth, to anyone wondering, is that even uni English courses in Japan are pretty meh. If a Japanese student seriously wants to improve their foreign language (unless they are like super skilled naturally, in which case they might get far enough with self-study and/or private tutoring)...
@beperov I beg to disagree regarding the classification of "terrorists". Terrorists are most importantly self-proclaimed. You can't be a terrorist if what you're doing is not with intention to cause terror. Yes, it can be even "terror for good means", but that's where the difference lies.