The latest forecast by Statistics Korea puts the population in 2072 at 36.2 million, a 30% decline from the current 51.7 million, even though the fertility rate may recover a bit to 0.68 in 2026. The population is expected to fall every year starting in 2025.
Nor to have one of the longest and hardest military services in the world.
Having North Korea as their only neighbour doesn’t help though