The same thing happened in France when American GIs were stationed there during WWII. I'd recommend "What Soldiers Do" by Mary Louise Roberts if you're interested in the details.
"It’s a long-buried part of South Korean history"
This is factually wrong. The geopolitical driven sex trade is a big issue in common Korean discourse (e.g. newspapers, social media, politics, etc). I would say that it and the historical victimhood native are overemphasized in Korean society. They are a strong country now, no need to ruminate in the past.