It's not just the number of cases that differ due to different testing regimes. Another difference is that Italy did some post-mortem testing to identify cases

It's not just the number of cases that differ due to different testing regimes. Another difference is that Italy did some post-mortem testing to identify cases that were wrongly reported as flu etc. but were covid19. I assume they were included in the number of dead. I don't know if they did the same in South Korea. Numbers sometimes are difficult to compare.