If your visitors are located in Korea or nearby countries for example Japan, Or you want to market your products to Korea it is wise to have your website hosted in South Korea. Download specially upload will be much faster and some search engines will give better ranking for local visitors.
If you already have a host in US or anywhere else and want to keep it there then you can only host a subdomain of your website in Korea so visitors from Korea can be redireted to that subdomain. We will be glad to help you contact us today.