My House Became Independent Because It was Said to be Useless!

Flora, the daughter of the western frontiers Margrave, came back from the battlefield to find out that her fiancé wishes to annul their engagement. It didn't really matter to her, but what did that foolish prince mean by "a worthless nobody of the Margrave's family on the edge of civilization?" And while there are signs of a conspiracy in court, even worse news about the invasion of demons arrives from the territory.