Maribelle, an ordinary small-town girl, gets entangled in an argument with a knight named Austin while trying to protect her younger brother. When Austin demands 10 Gold Coins for his trouble, Maribelle refuses, only to be taken aback by her father offering Maribelle in place of his only son for the unpaid compensation. Despite her refusal, Maribelle is forced into Austin's carriage, uncertain where she is being taken. Much to Maribelle's surprise, however, she arrives at the neighboring hostile kingdom of Mercens. Waiting for her is Princess Ilse, who looks identical to Maribelle! But what is it that Princess Ilse wants from Maribelle? Could there be a reason for her to summon Maribelle to the kingdom of Mercens? And does it have anything to do with the rumor about Princess Ilse and Prince Andrea's marriage?