Nigashita Sakana wa Ookikatta ga Tsuriageta Sakana ga Ookisugita Ken

逃がした魚は大きかったが釣りあげた魚が大きすぎた件

Born into a legendary ducal family, martial prodigy Maria “Mimi” Annovazzi loses her claim as heir and is suddenly ordered to marry into prestige. With no options left in her homeland, she transfers to a neighboring kingdom—only to be publicly dumped at graduation by a prince she’s never met over an engagement she didn’t even know she had! Will Maria be doomed to the life of a spinster?!

(Source: Crunchyroll)