Woah.
Where I live its 16 (although there was a movement to raise it to 18 but it failed).
I was actually surprised by S Korea's given the rest of Asia'e consent laws.
It is crazy how we base maturity, because I'd wager most even at 16 or even 18 and EVEN some at 21 are still VERY immature. It really does just depend on how you were raised, what you know, what you've experienced, etc.
Because while in places like Japan or China, somewhere in the Middle East, some of their laws are all the way down to 14 with I think the lowest on the planet being 12 or 13. Most people in the States would find that TERRIBLE but if you went to that country suddenly you're NOT creepy for thinking otherwise because the law said so.
Though from what I've heard, that may not be true...I was just speaking from a legal perspective. I've heard from places with low age of consent laws that while it IS legal, most people would still find it odd if you were "engage" with someone of that age.