Katsute wa Akuyaku Reijō deshita ga, Ima de wa Rippa na Ojisan desu (Webcomic)

Lady Adriana Ella Istria was once hailed as the most beautiful girl in the Kingdom of Rigatoni. Exiled from the country after "her" engagement was called off by the crown prince, 18 years later "she" transformed into a magnificent older man. Having been freed from the rigid life of a "duke's daughter", he lives a carefree life as an archaeologist on an island with his grandfather, but the girl who caused the crown...