Crane Wife/Origin

Origin
Crane Wife is based off on Tsuru no Ongaeshi (鶴の恩返し?, lit. "crane's return of a favor"). It's a story from Japanese folklore about a crane who returns a favor to a man. A variant of the story where a young man marries a young crane is known as Tsuru Nyōbō (鶴女房?, "crane wife").

The story tells that once upon a time, there lived an elderly couple in a certain place. On a snowy day in winter, the old man was going to town to sell firewood, when he found a crane that was caught in a hunter's trap. Feeling sorry, he released the bird from the trap. That night while the snow fell violently, a beautiful girl came to the couple's house. According to her explanation, ever since her parents passed away, she had been traveling between relatives she had never met before, when she got lost and as a result would like to stay for one night. The couple heartily welcomed her into their home. The snow had not quite stopped the next day, and the day after that, as the girl remained in the house of the elderly couple. Meanwhile, the girl tirelessly took care of the couple, making them happy. One day, the daughter asked the couple, instead of sending her off to meet relatives she had never met before, to please make her their daughter. The elderly couple was delighted to accept.

As she continued to help the old couple, one day she requested: "I would like to weave a cloth so please buy me yarn". When she was handed the purchased yarn, she stated: "please don't ever look in the room" to the couple; then hid in the room, and wove for three days straight without a break. "Sell this, and buy me more yarn", she told the couple. The cloth was very beautiful, and became the talk of the town immediately, and sold for a good price. With the new thread that was bought with the new money, their daughter wove another fabric, with stunning workmanship, selling at a higher price, making the elderly couple wealthy.

However, when she confined herself to the room to weave a third piece, while the couple persevered in keeping the promise at first, they began to wonder how she wove such beautiful cloth. Unable to fight curiosity, the old lady took a peek inside. Where there should have been a single girl was a single crane. The crane plucked its own feathers to weave between the threads to produce a glittering cloth. Large portions of the wing has already been plucked out, leaving the crane in a pitiful state. In front of the shocked elderly couple, the daughter who finished weaving approached them, confessing that she was the crane that was saved. While she intended to remain their daughter, she had to leave, as her true identity has been discovered. She turned back into a crane and flew into the sky, leaving behind the remorseful elderly couple.

In "The crane wife", a man marries a woman who is in fact a crane disguised as a human. To make money the crane-woman plucks her own feathers to weave silk brocade which the man sells, but she become increasingly ill as she does so. When the man discovers his wife's true identity and the nature of her illness, she leaves him. There are also a number of Japanese stories about men who married kitsune, or fox spirits in human form (as women in these cases), though in these tales the wife's true identity is a secret even from her husband. She stays willingly until her husband discovers the truth, at which point she abandons him.