In a fantasy version of Meiji-era Japan, the country is in a constant state of change and chaos with the coming of the Black Ships and the opening of Japan to the rest of the world. It was a time when anything could happen, and probably did.
On the southern island of Kyushu, two children who can turn into birds live with their adopted human parents. An evil feudal overlord kidnaps Azuki for the valuable white and orange feathers she sheds when she is a Toki-bird. Her courageous father dies trying to prevent her capture. With the help of the local birds and animals, her mother sets her free, but is also killed by the overlord’s men. With her parents dead at the evil overlord’s hands, a heartbroken Azuki flees. It’s all her fault! It’s her ridiculous ability to turn into a Toki-bird that caused everything horrible to happen! She destroyed her human family. Maybe she’ll do better as a bird. She’ll join her Toki-kin and give up being human at all. That will make things better. Won’t it?
Shota, her brother, can turn into a sparrow, but nobody’s interested in his plain brown feathers. The best he can do is follow his mother’s directions and rouse his own bird-kin to help his sister fly free. But his mother is hurt! She is dying, and Shota can’t think about anything else. But before she dies, their mother tells him all is not lost at home or in the human world for either of her children. She will do whatever she can to help them, living or dead, and she makes of Shota a final request. Shota speeds after Azuki to tell her that they will lose their human inheritance and won’t be able to live in human society at all, ever, unless they return in time to claim it, and return they must, honoring their mother’s wishes. Shota plans to bring Azuki home whether she likes it or not. She is his sister! They must stay together! There must be a way for them to embrace their heritage, all of it — didn’t their mother tell him so?
In her desperate search for her Toki-kin, Azuki visits egrets who send her off to the major Toki nesting grounds on Sado-ga-shima, far from their Kyushu home. On the way to a place she doesn’t know, unsure of her welcome, and with no clear directions other than “north and east”, Azuki weathers storms, encounters a fierce mountain ogre, and befriends a dragon who also has a secret. Will she ever reach her goal? What will she find when she gets there?
Shota, smaller and slower, doggedly follows the directions from the egrets. In a dream, his late father comes to give him help in his quest to track his sister and bring her home. Shota thinks he knows where Azuki is going, but it’s far from a sure thing. She could join other Toki, she could make a wrong turn, she could give up the idea and do something else! Can he find her? Will he reach her in time? Even if he does, can they possibly get back before the deadline? He is helped on the way by sailors, finding in himself a love of the sea, makes a friend of a war-horse, earns some gold, and just maybe discovers a way to get them back in time to claim their human heritage, so they can live as themselves, even if that isn’t like anybody else.