His timing was ideal. Trump had recently dropped his line about fire and fury. The US president followed that with a fusillade of tweets about his “nuclear button.” Go’s shop was soon fielding dozens of calls each day.

“For the most part, my customers are very conservative,” Go says. “They’re rich, basically. Because they can (afford to) build a bunker under their houses.”

His priciest bunker runs about $37,000. That buys a roughly 600-square-foot sanctum, complete with four beds, a sink trickling out purified water, an electrical system powered by a hand crank and an air purification system that can filter out radiation.

Imagine a small studio apartment with rounded steel walls, as in a submarine, with an entrance hatch that’s heavy as a bank-vault door. To make the bunker fully nuke-proof, he says, it must be buried underground and encased in cement.

Reporter Patrick Winn gives a tour of a custom bunker.

“My clientele tend to be people in their 60s or older who might have memories of the war,” he says. “Often they want to provide bunkers to their sons or daughters.”

Those old enough to recall the aftermath of the Korean War can be forgiven for shivering at any mention of a redux. Between 1950 to 1953, parts on the peninsula were turned to veritable seas of fire, largely thanks to more than half a million American bombs.

As Curtis LeMay, the US Air Force general overseeing the aerial campaign, put it:

“Over a period of three years, we killed off — what? — 20 percent of the population of Korea as direct casualties of war or from starvation and exposure.”

That these horrors exist within living memory might explain why some elderly Koreans feel especially jumpy over Pyongyang’s bombast — or aggressive tweets sent from the White House. Go has noticed that calls have spiked when either side makes threats.

But there is a flip side to this war panic economy. When fear runs hot, it thrives. But when peaceful vibes pervade, it practically collapses.

Images of Trump and Kim Jong-un shaking hands have been great for lifting the blanket of dread over South Korea. But for any business that relies on war angst, peace is poison. Go has sold 10 bunkers since he opened, but once Trump and Kim became friendly, interest plummeted.

Not that this is altogether bad, Go says. “That handshake is a very, very good thing. A peace mood has come to Korea.” He has since taken to emphasizing the merits of owning a bunker during a Fukushima-style nuclear meltdown or a tsunami.

He’s been quoted in a UK tabloid, The Mirror, as saying that he is “wishing (Kim Jong-un) presses the button and shoots the bomb” just to drum up his sales. Go says this quote is totally fabricated and that he does not, in fact, long for the nuking of his own country, which would make it tricky to run any business whatsoever — even one selling bunkers.