バリエーションを幾つか。
"When your study in the U.S. is over, you will come back to Japan, won't you?"
"Once you have finished your study in the U.S., you will return to Japan, won't you?"
"Upon completion of your study in the U.S., you will be back in Japan again, won't you?"
お礼
とても分かりやすい解説付きだったのでベストアンサーにさせていただきます。ありがとうございます(^^)