Cryptocurrency prices have long been higher in Korea due to exceptional demand in their market. This demand combined with the difficulty of arbitrage has historically caused the price differential.
https://www.coindesk.com/bitcoin-price-kimchi-premium-eroding/
There's some chance that this is just due to friction in the newly-regulated Korean market. Besides the ban on anonymous crypto trading, KYC/AML laws can slow down the inflow of cash.
Coindesk argues that this is a sign of normalization, which I agree with in the short term. If and when another serious bull rally happens, we may see an even more exuberant market. Should that happen, remember to take profit and stick to your investment strategy. Don't be the one who kept buying a $20,000 btc thinking the party would never end/