I think what you're asking is if you need a new metastore for your Korea data. 
The technical answer is no. You can just onboard the Korean storage account as an external location in your west europe based Metastore. However you can't onboard Databricks workspaces into the metastore that have its regions outside of the metastores location. If you plan on adding Korea to your data governance setup, you might want to consider seperating each region with corresponding data assets through different metastores.