Manga Grimm Douwa: Kaguya-hime

A young woman is sent to the mountains to live with her grandmother after her parents die. She is cared for by a woodcutter and his wife who take her in. One night, she overhears them discussing her fate and decides to run away. She meets a fox spirit who offers her a deal: he will help her escape if she agrees to become his wife. She accepts, and they travel to his home in the mountains. There, she learns that he is a powerful spirit who has captured many women before her. She must use her wits to survive and find a way to escape.