Juujin Taichou no (Kari) Konyaku Jijou

A member of the beastkin nobility and the heir to the Bearwolf Marquis, Leold, suddenly bites Katie on the shoulder, branding her with a "Mark of Proposal". Katie, who was crossdressed at the time, is mistaken as a male and dragged into being his fiancée for a few years until the mark disappears...