Over at the Korean Law Blog the actual ROK law is posted in regards to self defense. Of interest is that if you ever got in a struggle with someone trying to kill you that required you to defend yourself to kill them you most likely get prosecuted for it:
Regrettably to many, Korea interprets the preceding Article 21 of Korea’s Criminal Act very narrowly. There is, only, one reported cases in the past 25 plus years where someone accused of murder has prevailed in a claim of self-defense. The only case I can find is the notorious Kongneung-Dong Murder Case. The case involved a break-in to a home that lead to the death of the burglar. The burglar was armed and he killed one person in the apartment.
The accused claimed, inter alia, that his act of killing the burglar was performed to “prevent impending and unjust infringement” (more injuries) of his “legal interest”(his life). He claimed that his only means of protecting his life was his actions. Additionally, the act of the burglar was at night.
The following charges still lead to charges by the police. The prosecution decided not to indict. [Korean Law Blog]
You can read more at the link, but the moral of the story is that if you have to defend yourself in Korea use as little force as possible even if someone is trying to kill you. A perfect example of the negative consequences that can happen is the 2004 Shinchon Stabbing Incident or the 1995 Seoul Subway Brawl. In these cases the GIs were punished for defending themselves while the Koreans that started the fights got away with no legal consequences.