Doinaka Shusshin no Imo Reijou, Nazeka Koushaku ni Dekiai sareru

To maintain her baron family's reputation, Vivi, a young lady from the countryside, comes to the royal capital to work. Despite being a seamstress, she's a practical, no-frills country girl. One day, Vivi has a chance encounter with Alec, the captain of the Holy Knights, and—shockingly—he falls in love with her at first sight! Even though Vivi is bewildered, Alec's overwhelming affection doesn't stop, and before she knows it, they end up living together!? It seems there's a deep reason behind his actions, but romance-clueless Vivi can't make sense of it at all... "I promise I will make you my wife." The unwavering love of a cunningly charming duke is far too much for a humble country girl to handle! (Source: Kadokawa, translated)