No Blessings for You
You would be pretty surprised to sneeze around a group of people with nobody having the courtesy to say “bless you”. It’s become second nature for Americans to respond to a sneeze in this way. Having your sneeze be completely ignored is something you would have to get used to in South Korea.
The term “bless you” is unheard of. You’re not going to hear it and you shouldn’t say it to someone who sneezes, even though it may be easy to slip. If a South Korean traveled to the Western countries, they wouldn’t understand someone responding to their sneeze in this way.