The hero Soujuurou (草十郎) starts the story as a teenager fighting on the Minamoto side in the Heiji Rebellion of 1160. He has a lonely childhood behind him. His mother, a flute player, died in childbirth, and his samurai father's family did not want this child from a different mother, so that he was raised separately and grew up a lonely child, playing the flute he inherited from his mother in the hills where no-one could hear. The rebellion does not go well for the Minamoto; and the story begins with the final battle, and subsequent flight of the defeated forces. This desperate journey is very well described; and we share the experience of the young Soujuurou, as he and the young Minamoto boy he accompanies, Minamoto no Yoritomo, slowly realise that the defeat was more than a setback and that everyone they meet from now on is potentially their enemy.
Soujuurou still feels despair and has no meaning in his life after the defeat of his side. Learning that Yoritomo has been captured and is being taken to Kyoto for execution, he prepares to attack the Taira forces accompanying him, in effect throwing his life away. Before he can do so Itose seeks him out again and persuades him to help her dance once more, in an effort to change Yoritomo's fate. The magic is successful and Yoritomo's judgement is changed to exile in Izu; but the magic has been noticed. Soon various powerful nobles in Kyoto are looking to find the two performers for their own purposes.
The fantasy element of the story is largely limited to the effects of the flute and dance. But there is also a talking crow who is a major character. Soujuurou's flute playing draws wild animals to him, much like Orpheus or Tamino in the west. (I don't know if Japanese culture has similar myths; but the book reads like a reworking of the Orpheus myth in other respects too.) The crow Torihiko Ou (鳥彦王) is one of the creatures that Soujuurou's playing attracts. The name means King Malebird. Among the crows, a line of divine descent often has female birds who can speak and understand humans. Males with such ability are rare and destined to become king. Torihiko Ou, accompanied by seven comrades, is seeking experience of the human world and chooses to accompany Soujuurou.
"Shrines where humans worship somehow just don't register, they just slip out of my head, whoosh, like that."
"Do birds have gods they worship, then?" Soujuurou asked.
Of course there were, the answer came back. "I know there are gods. I, after all, am a direct descendant of them."
"You .... you're trying to tell me that you yourself are a being that receives worship."
"What's that? Didn't you know? Torihiko Ou is the living god of the birds, pal."
While Soujuurou wondered whether, with that attitude and that language, "living god" was not going too far, the crow hopped onto his head and continued talking with great self approval.
Like many fantasies it's a long book. On the whole it manages its large story well; but occasionally it loses steam. There's a bit too much reliance on having third parties praise the two leading characters, rather than allowing us to get to see their qualities for ourselves. And the broader strokes of these two characters seem to come from familiar types in fantasy and Japanese popular literature. The greatest achievement is probably the combination of the fantasy with a Heian setting. That does mean that a non Japanese reader will have some hard going through pages filled with unfamiliar names, titles and objects.