Shougun Koushaku no Souteigai Mitsugetsu: Migawari Hanayome wa Amaku Midara ni Saku

A bride wanted only to give birth to an heir. An innocent nun. No love was ever meant for her... But she was sweetly and fiercely desired... "I'll prove to you how much I love you." Her honeymoon with Duke Rodalf, who dotes on her, is something that Chloe, a nun, hadn't expected. Rodalf, Chloe's first love, had chosen her beautiful older sister, Eleonore, as his bride. When her sister eloped with another man, Chloe suddenly became his substitute bride. All he wanted was an heir. She planned return to the convent and give up on her unrequited love after giving birth to a boy. However, when he took her to bed, what was supposed to be a duty was sweet and passionate, and her innocent body was filled with lust. Though she hesitated as her body and mind were melted by his hot passion, her resentment toward him began to melt away... (Source: BisouBisou Comics)