This is one of the famous stories, especially in the northern part of Japan, where many stories are concerned with winter.
Once upon a time, there was a young guy who lived on a mountain alone. He was kind and honest, and he always went to the mountain to hunt animals or to cut down trees, even in winter. One day he was going to the mountain. On the way, there was a crane lying on the ground, and it had broken her wing, so he went back to his house, holding her, and treated her very carefully every day. Because of his care, she could fly as well as in the old days, so he let her fly back to her home.
One day, it was snowing and cold. Someone knocked at his door. It was a beautiful young lady, and she asked him to stay for a night, because it was midnight. Of course he permitted her to stay. She didn't leave his house; however, she worked very hard for him, cooking, cleaning, etc. So he came to love her, and she loved him too, and one day they married.
One night she told him not to peek at her while she was working, and she went to another room to make clothes. He wondered why she had told him that, and he watched her shadow. The shadow was not the shadow of a human. So he made a hole in the door, and he watched her. Surprisingly, it was that crane who he had helped before. She was making clothes with her wings. He couldn't help but open the door; she was surprised and ran away from the house. Actually she flew away from his house.
He was never seen the crane since that day. We must keep our promises.