Dress na Boku ga Yangotonaki Katagata no Kateikyoushi-sama na Kudan

An ordinary boy called Sherlock Doyle is captured and forced to put on his twin sister's dress by the Emperor's diplomat to be shipped to a small country called Ehren. His genius sister, Glinda, went missing two days before she's supposed to be sent to Ehren to be an royal tutor for the King's child