Just to put into perspective, koreans currently make up roughly 0.7% of the world population....
Which makes it almost impossible that our MC, the sage, and the butane cans are all korean...
Compare that to US (easiest to get data) deaths, where flu and pneumonia make up 2% of all deaths...
RNG is RNG
Plot wise the book could've been written in a foreign/old language that our MC just happened to study when she was on earth, logic wise it becomes much, MUCH more plausible, and easier to explain away