Natsu is a boy who has gone through many hardships. First, his mother died. Then, his father got remarried to a "witch" of a stepmother, with two little horrors to call her own. And then his father disappeared, assumed dead. Now he works as a slave in his own household. The kingdom is holding a ball, to which everyone, including the villagers are invited. Natsu thinks this could be his chance to escape his stepmother and find another life, but plans change. He meets the prince only to fall in love with him and maybe he might be Natsu's happily ever after.
So, I basically got this idea from Cinderella, so the idea goes to them really. Thanks!