Caucasus: Nanatsuki no Nie

There is a small village. One day, two university students visit the village to do research about a local legend handed down from generation to generation. However, they are struck by snowstorm and saved by Benio. They are invited to her mansion and a strange wedding ceremony is held there... If a bride can spend one night in a coffin safely, their marriage will be completed. However, it is all destroyed by someone unknown...