Totsukuni No Shoujo

"It is a story full of sadness. From now let's recite a slow and beautiful story from long ago." Shiva, a young girl who loves to stroll about in the countryside, lives in a vacant village with her guardian, a wendigo-like gentleman. He forbids her from going outside, so she won't be cursed, but Shiva's curiosity makes her yearn for the outside world. What is this curse about?