Which Bitcoin app do Korean use?

I'm quite interested in the world of Bitcoin and I've noticed that South Korea has a significant presence in this crypto space. I'm curious to know, which Bitcoin app do Koreans primarily use? I'm asking because I'm looking to expand my understanding of the local crypto landscape and also to potentially use the same app for my own transactions. I've done some research but the information is scattered and often outdated. I'd appreciate it if you could provide me with a detailed answer, including the name of the app, its main features, and any unique aspects that make it popular among Koreans. Additionally, if there are any specific requirements or considerations I should be aware of before downloading and using the app, that would be helpful as well. Thank you for your time and assistance. I look forward to learning more about this fascinating topic from your expertise.