No Blessings for You
You’d be shocked if you sneeze in a crowd of people and no one says “bless you.” It’s become standard practice for Americans to reply to a sneeze in this manner. You would have to get used to the fact that your sneeze is not acknowledged in South Korea.
The phrase “bless you” is unheard of. Even though it’s tempting to say it to someone who sneezes, you won’t hear or say it. Someone from South Korea traveling to the West would be confused if they heard someone respond to their sneeze in this manner.