The mountains and forests of Japan have long been the domain of the legendary Tengu, one of the most famous and ubiquitous creatures in Japanese folklore. The Tengu was a shape-shifting bird-like creature of the sky and trees, and they were seen as a protector of the mountains. The Swan Maiden is a mythical Tengu like creature who shapeshifts from human form to swan form in Russian folktales. Similar to their neighboring Japanese folktales, a larger number are found to be males, despite the term "maidens".
The folktales usually adhere to the following basic plot: A young, unmarried man steals a magic robe made of swan feathers from a swan maiden so that she will not fly away, and winds up marrying her. Usually she bears his children. When the children are older they sing a song about where their father has hidden their mother's robe, or one asks why the mother always weeps, and finds the cloak for her, or they otherwise betray the secret. The swan maiden immediately gets her robe and disappears to where she came from. Although leaving the children may grieve her, she does not take them with her. If the husband is able to find her again, it is an arduous quest, and often the impossibility is clear enough so that he does not even try.
Animal Wives in Russia and Japan
This is a common motif in folk tales across the world, though the animals vary. The Italian fairy tale "The Dove Girl" features a dove. There are the Orcadian and Shetlandic selkies, that alternate between seal and human shape. A Croatian tale features a she-wolf. In Africa, the same motif is shown through buffalo maidens. In East Asia, it is also known featuring maidens who transform into various bird species. In Russian fairy-tales there are also several characters, connected with the Swan-maiden. In the Japanese legend of Hagoromo, it is a heavenly spirit, or Tennin, whose robe is stolen.
Another related tale is the Japanese myth of the Cowherd and Weaver Girl, in which one of seven fairy sisters is taken as a wife by a cowherd who hid the seven sisters' robes; she becomes his wife because he sees her naked, and not so much due to his taking her robe.
One notably similar Japanese story, "The crane wife", is about a man who marries a woman who is in fact a crane (Tsuru no Ongaeshi) disguised as a human. To make money the crane-woman plucks her own feathers to weave silk brocade which the man sells, but she becomes 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, 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.