South Korea is hostile for new families. Unless you were born to rich parents, have a decent education with a good job (that's with a Multi-national or a Chaebol), own property in Seoul, find a partner, and survive the probability of divorce, having a child is impossible--let alone having two to meet the population replacement rate. What's the solution?
It's honestly miraculous how far it's come. Within one lifetime, it went from a primarily agricultural economy to one of the world's largest and most industrialized. It builds (at times) half of the world's ships in tonnage, and its engineers and contractors are responsible for many of the world's tallest buildings.