Tuition is cheaper than other private schools, and because Busan is the second largest city, the living expenses should be higher.
Language training in schools is also possible. As long as he applies, his admission has a bottom line. In order to reach a certain level, he must learn English and Korean.
You must pass CET-4 before you can enter your major.
As for why medicine can't do this, I don't know, but there are still many majors in undergraduate courses, but there are no master's and doctoral courses.
The above is my personal opinion (I have been in Korea for two years and I am still not familiar with the university). For the specific situation, I suggest you consult your teacher and make a field trip if you have the conditions.