From Now On, My Husband Is Scheduled to Love the Saintess

Lady Reasel, a marquise's daughter, is chosen as the fiancée of Crown Prince Baldios. However, he is prophesied to be destined to marry a saint who will one day descend upon him. In this country, prophecies are absolute, and there is a custom that anyone who marries royalty will have their little finger turned to stone until they bear an heir. For this reason, everyone was reluctant to marry Baldios, but Reasel, a big fan of his, gladly accepted. Reasel is undeterred by the aloof Baldios, but through the process of trying to conceive a child, she begins to realize his true feelings...?

Source: AlphaPolis, Translated