Hidenka no Bishou: Migawari Hanayome wa, Hikikomori Denka to Shiawase ni Kurashitai

Is it wrong to seek the happiness someone else denied you?

Sara, a royal maid in the Kingdom of Saleilles, is ordered by the king to enter a political marriage with the eldest prince of their rival kingdom, Ferrier—but as the body-double of the real princess! But then Sara's boyfriend cheats on her with the princess she considered a friend and turns on Sara completely! Utterly betrayed by those she trusted most, Sara hits rock bottom, heart shattered...

Farewell, Princess I used to love and respect. Farewell, my once-beloved boyfriend.

So Sara makes a decision—she will find happiness in Ferrier no matter what! But that all hinges on her husband-to-be...a reclusive, misanthropic prince who has a slightly difficult personality and is constantly wearing a mask. To make matters worse, rumors are spreading in Ferrier of a terrifying black beast on the prowl...

Can Sara ever hope to find happiness in these conditions?!

(Source: Cross Infinite World)