30‑sai Toshiue Koushaku no Gosai no Hazu ga Sono Musuko ni Dekiaisareru

Serena, a down-on-her-luck aristocrat, supports her indebted family through sewing work. When Marquis Harding, a man thirty years her senior, proposes marriage and offers to settle all her family's debts, she accepts for their sake. Upon arriving at the Harding mansion, however, she is greeted not by the Marquis but by his son, Felix—a man widely admired by women. To her shock, she learns that her intended groom is Felix himself, not his father. Braced for coldness and rejection, Serena is instead met with Felix's overwhelming and ardent devotion.