Jonathan Knight, who lives in north Japan, spoke of waking up to the dramatic news a nuclear missile had been fired by Kim Jong-un.
Speaking on Victoria Derbyshire on the BBC, Mr Knight said: “It woke me up. I was fast asleep, two minutes past six. There’s a system in Japan called J-Alert and that’s like getting an SMS on your phone, whether you like it or not.
“That message said in Japanese ‘missile launched, missile launched’.
“The audio that you just played is the same J-Alert system that operates across Japan and that was saying the same thing, that you could just hear in the background of what you played, some speaking.
“That speaking was saying ‘missile launched, missile launched’ and it says to take cover, go to a basement or a strong building, and that’s what woke me up.”
Told he sounded calm, Mr Knight replied: “There’s a sense of calm here. As you go round the streets today and drive round, everybody’s gone to work as normal, kids went to school.
“There was a second message about 15 minutes after that that said that the missile had passed over and had landed about 230 km from where I live.
“That message also said not to touch any fragments if you saw anything like that but to report it to the police.”
South Korea’s military said Kim’s regime fired the “unidentified projectile” from Pyongyang towards the sea at 5:57am local time.
The Japanese government’s J-Alert warning system advised people in the area to take precautions.
Warnings were issued across Hokkaido, Aomori, Iwate, Miyagi, Akita, Yamagata, Fukushima, Ibaraki, Tochigi, Gunma, Niigata and Nagano.
But public broadcaster NHK said there was no sign of damage and the Japanese military did not attempt to shoot down the missile.