

Two families, the Sun herd live by day and sleep by night, they rule the plains. The Moon herd lives by night and sleeps by day, they rule the forest. The two are feuding over something... (It could be over territory, annual games inspired by the pokemon world, spiritual beliefs???? or it could ancestral thing and as the reasons to despise each other fade, it just sticks for the sake of history.)
The newer generations of both herds are growing ever more curious of one another, especially the children of the leaders.
Memory, the daughter of the Sun herd leaders, spots shadows dancing behind the trees one night. She becomes fascinated by them, staying awake until the moon is high in the sky to watch them. Their glowing eyes and markings mesmerising and beautiful. She watches from where her family sleeps for some time, until finally one night she finds the courage to approach the border but she never passes. One of the shadows seems to linger by her. When it moves, she chases it and when she moves, it chases back. The shadow is Sin, the son of the Moon Herd leaders. The two form a forbidden, yet strange friendship, even though they have never met face to face, or likely ever will (So they thought).
Memory expresses her fascination of these shadow creatures to her parents, it doesn't go well. Receiving an unexpected scolding and being warned of ever approaching them. She refrains from telling them of the new friend she has been playing with and sulks the rest of the day.
When that night came, she gathered the courage to break the border and finally meet her new friend face to face. No more chasing shadows... However when she beaks the tree line and starts wandering deeper, she hears the enchanting song of the carousel. Distracted by the melody, she follows it's call and stumbles upon the mystical members of the carousel. Completely mesmerised by these as well, she follows them and minutes turn in to hours and hours become days and when she finally realises that she is far from home, with no way of knowing how to get back, she decides to stay in their company and join them. Hoping one day they will return to the forest and she can return home.
Sin has witnessed this but because of the old tales and his families teachings, dares not stop or approach her. He returns home, saying nothing.
When her family realises she has gone, they immediately storm the forest and accuse the Moon Herd of taking her. They argue and squabble and that is when Sin admits what he has saw. The Sun herd leaders, infuriated that the Moon herd leaders son didn't do anything to stop her, demand that they send only their best to find and retrieve her. (Either they do or they refuse.) Sin offers to go however still being too young, his family denies him this task.
Never forgetting, Sin waits until he has come of an age where he can fend for himself and sets off to find the lost princess. (This is where the inspiration of Andrew Lang's tale 'Minnikin' comes in to play. Having to undergo a series of trials to gain information of her whereabouts. Minnikin continued to meet the old hag in his story, stealing her false eye and when she asks for it back, he asks what she would give him in return for it. These would be things that would benefit and help him in the future.)
Everyone he comes across gives him very little, telling him that he can't just find the carousel, as everyone has heard stories but has never actually seen them, that you just 'happen' upon it. Though one day he comes across someone who has seen the princess, assuming it is her from the description he gives at least, performing her stories. One story being of the tale of two herds at war and two children, friends, caught in the middle of it. They also tell him that if you listen closely enough, you can hear her singing to the moon just before the dawn.
Knowing this is her, he asks to be pointed in the direction they had last seen her in and off he goes again. While on his travels, he could hear her song, a mournful tune. When they finally meet again, it could be while she is performing. During it, she spots him but waits until after the show to approach. She would know those glowing eyes and markings anywhere. Overwhelmed with joy, nerves and fear, the happy reunion falls in to sorrow when he offers to show her the way home. She explains that she is unsure whether you can ever leave the carousel and that if they were to return, they would never be allowed to see each other again and instead, offers him a place in the carousel so that they can be together. (As friends, or as lovers, depending. xD )