[Nyororin]

Someone in Korea without a valid Japanese working visa is no different than someone staying in the hotel next door on a tourist visa. You still have to do the exact same thing to hire them. There is no particular disadvantage to hiring someone who happens to be in Korea at the time - and in this case an advantage as all the qualifications were there.

You don`t need to speak Japanese to teach English in Japan. I`d even say that it`s to your advantage NOT to - as a lot of places don`t want to risk you speaking to the students in Japanese rather than 100% English.