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

Serena is a poor aristocrat who works as a seamstress for her family, who are in debt. She receives a marriage proposal from the Marquis of Harding, 30 years her senior, who offers to cover all her debts. She accepts the proposal for the sake of her family and goes to Harding's mansion, but there she meets his son, Felix, who is the object of many women's attention! It seems that the man she should marry is not the Marquis, who is 30 years older than her, but his son, Felix...! She thought he was cold, but for some reason he dotes on her. Source: MU