Lake Kussharo has a circumference of 57km, making it the largest lake on the island of Hokkaido and the second largest in Japan. It formed in a gigantic old crater, to the east of Akan National Park. Its deepest point is 118m and its centre is taken up by the immense island of Naka-jima (12km circumference), the lair of a local monster dubbed Kusshi, whose silhouette, reminiscent of the Loch Ness Monster, can be seen from Sunayu beach.