I would give the same general advice. Be honest and say "Hey, I am applying for these specific jobs. If I don't get them, I would want to stay here. I am applying because these jobs are jobs that give me the chance to stay in Korea longer and experience more teaching with a different age group. I like it here a lot, but I do want to see if I can work with a different age group."
That kind of thing. Be nice about it. If you talk to your CT, bring some coffee or something fun. Don't make it sound like you are going to quit your contract or anything like that. And make sure that you let them know that you are very interested in the school you are currently at and that you hope it doesn't offend anybody.
Be polite about it, sincere, and gentle. Do tell them...