Gakeppuchi Reijou ga 4-ri no Nakama to Tomoni Ouhi ni naru made

With her territory facing a crisis, Countess Estelle is on the brink of collapse. She resolves to overcome the current situation and rebuild her territory, no matter what. To get the funds she needs, she takes a gamble and heads to a casino with her eccentric friends, but things take an unexpected turn— before she realizes it, she's become the prince's fiancée!?

(Source: Comic Walker, translated)