An interesting concept, but it's actually very long until we get to the only interesting part: the ceremony. With an interesting twist. Is it easier or worse that the parents get to choose ? We don't see it but, the consequences of the [spoiler]swap[/spoiler] are interesting too, [spoiler]knowing that she was the one chosen to die, and will probably be blamed for the death of her sister[/spoiler]. How do you go on with that ? That would have been more interesting than the long intro.