It's become a sort of joke between me and my Korean friends in Seoul. Each time after a major North Korean provocation — this time, Pyongyang's fifth nuclear test — I'll message them and ask: "How about now? Nervous yet? How about now? Now?"

Each time, including this one, the result of my informal survey is the same: It's business as usual here.

Turns out, the one place in the world that's not on edge about North Korean dictator Kim Jong Un's increasingly scary militarism is South Korea. "It would take a North Korean missile landing in Seoul to change things," one Korean friend told me.