At His Majesty's Convenience: Harlequin comics

Jake, a young businessman in New York, is called back to his homeland, Ruthenia, to succeed the throne and is followed by his personal assistant, Andi. Three years after the rebuilding of his country, Jake is pressured by this staff to get married within the month, by Independence Day. But at the daunting party where Jake must choose a future queen from the women of numerous powerful families, Andi gets into an accident and loses her memory! Unlike her usual brilliant but straitlaced self, Andi becomes naively charming. Then one day, the two are caught together by the media and Jake publicly announces that he is “engaged” to Andi.