I bet it it is the time difference which is causing the lack of communication. That is a 180 degree time shift. When they are awake you are asleep and vice versa.
Not sure if it may help in the short term but it may be an interesting idea to start a diary of your thoughts and feelings throughout the days while they are gone? Treat it as an intellectual excercise. Later you can examine and analyse your writings. It might be useful to you later on during the Korea/Japan thing.