Kohakushoku no Kishi wa Seijo no Hidarite ni ai wo Chikau

The black knight, Quill, is suddenly asked to marry the country's saint, Linetta Series. Hoping to escape the prospect of marriage, he accepts the ill-suited proposal, but she has lost her emotions as the price of her role as saint. His days with Linetta, whose emotions are unreadable and like a beautiful doll, unexpectedly stir his heart... When a knight who has given up faith meets a saint who has forgotten how to feel, their destinies begin to quietly waver. (Source: Kadokawa, translated)