I don't entirely agree with your viewpoint here! South Korea is the third largest country in terms of transaction volume, just behind Japan and USA. If (in worst case) South Korean government decides to ban all crypto exchanges and declare it illegal, a huge impact will be seen in the market during the exit period. Even though the impact will be temporary, there's no way we can escape that! No matter how decentralized the market is!
South Korea is a closed market. No one else can get in or out. Most of the exchanges there seem to be bent or incompetent so I wouldn't choose to believe their volumes either.
If they threw it in the only tangible effect beyond sentiment might be more supply released to the rest of the world but the South Koreans love alts more than most places shitcoins would have the biggest aftershock. At one point, quite amazingly and relatively recently, Bitcoin Gold had higher volumes than Bitcoin.
There'll be a reasonable ripple perhaps but then it'll be shrugged off. South Korea is no great loss.