If your trip to Mashu Onsen is all organized but your itinerary is a little on the empty side, let us give you a helping hand.Stop by Kussharo-ko. It's one sight you'll find on many visitors' to-do lists. If you still have some room on your itinerary, Mount Io and Kawayu Onsen Kawayu Kosyu Yokujyo will keep you occupied as well.