Inakamono ni wa Yoku Wakarimasen Bonyari Henkyou Haku Reijou wa, Danzai sareta Koushaku Reisoku wo Omochikaeri suru

Cynthia, the daughter of a margrave, grew up carefree in the vast countryside home to the kingdom's best army. One day, while enjoying her usual romantic novels, she attends her first evening party in the royal capital. There, she witnesses the story of a duke's son being condemned by a selfish princess and having his engagement broken off! Seeing a scene straight out of a novel, Cynthia bursts out and blurts out, "Then marry me!"

(Source: Kadokawa, translated)