According to Wikipedia., 46% of Koreans cite no religion/atheism. This is seen as a great opportunity for those proselytizing. Christians have been converting Buddhist here since the 1800's and, if considered jointly, are the biggest block of believers. There are about 70 Mormon missionaries in Daegu area now trying to convert Koreans. They wanted to have a chat with me...talk about barking up the wrong tree.
Korea, like most countries that were originally Buddhist, is very open to other religions. At my school, every Saturday there are people proselytizing. There is a weekly newspaper written by a ministry that is provided to the students. I can not read most of it, but the students tell me there is some mention of religion, but that is not the focus of the paper.
I often wonder about these things. Somehow it is OK to promote some religions, Christianity primarily, but I wonder how people would react if the same things were being done in the name of Islam or Atheism.