Wiggling my way out of a friend's plans.

I've been traveling with friends for the first time in (South)Korea and Japan, and while at first I thought I would really enjoy their company, after a week in Korea I've come to realize that being with them in Japan would ruin my trip. They're critical, negative, constantly bicker, stress endlessly about doing things just the way they planned ahead of time and seemingly have no real interest in actually experiencing the places they go to. I can't stand touring with them, but they've already made all of our plans ahead of time and I'm expected to join them in everything we do, is there any way for me to spend as much time away from them as possible so that I can actually do my own thing and enjoy this trip.