Your sense of history is shallow if WWII is the farthest back you know. But there was no systematic killing or torturing of Koreans in WWII. Colonial rulers don't do that to the local population. Japan did not invade Korea in WWII if you don't know your history. Korea was annexed, not by force but by treaty, into Japan 30 years before, so the Japanese taking of Korea wasn't by guns and bloodshed. And apparently, the Korean population doubled from 13 million to 27 million during the 35 years of Japanese rule. I wouldn't imagine Japanese rule to be any more benign than any other European colonial to its colonies, but at least in terms of mouths fed, the rule would be quite the opposite of murder.