There are no National Guard units stationed in Korea.
How long is your study abroad program? Talk to your chain of command about how to work this. If it's just a few months, you could split-train one month ahead, and one month behind, and then get approval for an excused absence for the drills in the middle. You may not have enough drills to make a creditable year for retirement (which doesn't matter now, but you'll care a great deal in a few years). If it's a longer period, you may request for up to a year in the Inactive National Guard (ING). You get no pay or benefits, and your time does not count towards any contractual obligations.
Address this issue at once, even if it's just a possibility. The longer in advance you work this out, the easier it will be. People get very crabby when you surprise them with complex issues.